Method and terminal for transmitting power headroom report in dual connection between terminal and base station

ABSTRACT

One disclosure of the present specification provides a method for receiving downlink data in a wireless communication system supporting 256 QAM. The method for receiving downlink data in a wireless communication system supporting 256 QAM comprises the steps of: receiving configuration information about power back-off; receiving downlink data transmitted on the basis of the configuration information about power back-off; and demodulating the received downlink data on the basis of the configuration information about power back-off, wherein the configuration information about power back-off may comprise information related to at least one of the following: whether to apply power back-off, the reduced amount of power of downlink data by power back-off, a frame index to which power back-off is applied, a subframe index and a resource to which power back-off is applied.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2015/003133, filed on Mar. 31, 2015,which claims the benefit of U.S. Provisional Application No. 61/974,992,filed on Apr. 3, 2014, 62/002,187, filed on May 23, 2014 and 62/034,793,filed on Aug. 8, 2014, the contents of which are all hereby incorporatedby reference herein in their entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to mobile communication.

Related Art

The 3rd generation partnership project (3GPP) long term evolution (LTE)evolved from a universal mobile telecommunications system (UMTS) isintroduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequencydivision multiple access (OFDMA) in a downlink, and uses singlecarrier-frequency division multiple access (SC-FDMA) in an uplink. The3GPP LTE employs multiple input multiple output (MIMO) having up to fourantennas. In recent years, there is an ongoing discussion on 3GPPLTE-advanced (LTE-A) evolved from the 3GPP LTE.

As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 10)”, 3GPP LTE/LTE-A may divide the physical channel into adownlink channel, i.e., a physical downlink shared channel (PDSCH) and aphysical downlink control channel (PDCCH), and an uplink channel, i.e.,a physical uplink shared channel (PUSCH) and a physical uplink controlchannel (PUCCH).

Meanwhile, Power Headroom (PH) information of a terminal can be used toform a method for a base station to utilize resources of a terminalefficiently. Power control technology (or power adjustment technology)is an essential element for minimizing interference and reduce batteryconsumption of a terminal to achieve efficient distribution of resourcesin wireless communication. If a terminal provides PH information to abase station, the base station can estimate uplink maximum transmissionpower that a terminal can tolerate. Then the base station can provideuplink scheduling such as Transmit Power Control (TPC), Modulation andCoding Scheme (MCS), and bandwidth to the terminal within the estimateduplink maximum transmission power.

Also, a situation in which cells or cell groups at different geographiclocations exchange signals or channels related to control and/or datacan be taken into account in the next version of the system.

At this time, scheduling information among cells or cell groups atdifferent geographic locations may not be shared dynamically but can beperformed independently; in this case, transmission of each UplinkControl Information (UCI) to the corresponding dedicated cell can betaken into account.

In other words, transmitting UCI about a first base station (eNodeB1) tothe first base station and transmitting UCI about a second base station(eNodeB2) to the second base station can be taken into account.

In this case, it can be described that duel connectivity has beenestablished for a terminal connected to both of the first and the secondbase station.

However, in the case of dual connectivity, how a terminal transmitsPower Headroom Reporting (PHR) to the first or the second base stationis still left unsolved.

SUMMARY OF THE INVENTION

Accordingly, the disclosure of the specification has been made in aneffort to solve the problem.

To achieve the objective described above, a method for transmitting PHR(Power Headroom Report) in a wireless communication system. The methodmay be performed by a terminal with dual connectivity to an MCG (MasterCell Group) and SCG (Secondary Cell Group). The method may comprise:triggering a PHR about a serving cell belonging to the MCG on the basisof a PHR triggering condition; and if the PHR is triggered, transmittingthe PHR to a serving cell belonging to the MCG. The PHR may include PH(Power Headroom) information corresponding to an activated serving cellbelonging to the SCG, and PH information corresponding to the activatedserving cell belonging to the SCG is either virtual PH information oractual PH information determined on the basis of scheduling informationof the terminal.

Also, the virtual PH information can be calculated on the basis of apredetermined reference format.

Also, the PHR triggering condition can include a first PHR triggeringcondition and a second PHR triggering condition. The first PHRtriggering condition may includes a case in which the“prohibitPHR-Timer” is expired or has expired; a case in which aterminal secures uplink resources for new transmission; a case in whichany one of activated serving cells configured for uplink has resourcesfor uplink transmission, or PUCCH transmission exists in thecorresponding cell after uplink data transmission through the uplinkresources in the corresponding TTI or after the last PHT transmission isperformed at the time of PUCCH transmission; and the case in which thechange of power backoff request value (P-MPRc: Power Management MaximumPower Reduction) is larger than the “dl-PathlossChange” [dB] value afterthe last PHR transmission. The second PHR triggering condition mayinclude a case in which the “prohibitPHT-Timer” is expired or hasexpired; a case in which a terminal has secures uplink resources for newtransmission; and a case in which the path loss after the last PHRtransmission has been performed is larger than the “dl-PathlossChange”[dB] value about at least one activated serving cell used as the pathloss reference.

Also, PH information corresponding to an activated serving cellbelonging to the SCG can be configured to have the virtual PHinformation in case the PHR is triggered according to the first PHRtriggering condition.

Also, the virtual PH information can be transmitted together withP_(CMAX,c) value which is the maximum transmission power of a terminalwith respect to a serving cell c to which P-MPRc has been applied.

Also, the V field of PHR MAC can be configured to be 0.

Also, in case PH information corresponding to an activated serving cellbelonging to the SCG is configured to have the virtual PH information,the first PHR triggering condition can be ignored.

Also, in case PH information corresponding to an activated serving cellbelonging to the SCG is configured to have the virtual PH information,the second PHR triggering condition can be satisfied even when aterminal has not secured uplink resources for new transmission.

Also, whether the PHR is triggered according to the first PHR triggeringcondition can be determined through a higher layer signaling.

To achieve the objective described above, a terminal for transmittingPHR (Power Headroom Report) with dual connectivity to an MCG (MasterCell Group) and SCG (Secondary Cell Group) in a wireless communicationsystem. The terminal may comprise: an RF unit; and a processor fortriggering PHR about a serving cell belonging to the MCG according toPHR triggering conditions. If the PHR is triggered, the processorcontrols the RF unit to transmit the PHR to the serving cell belongingto the MCG, wherein the PHR includes PH (Power Headroom) informationcorresponding to an activated serving cell belonging to the SCG, and PHinformation corresponding to the activated serving cell belonging to theSCG is either virtual PH information or actual PH information determinedon the basis of scheduling information of the terminal.

To achieve the objective described above, a method for transmittingtransmit PHR (Power Headroom Report) in a wireless communication system.The method may be performed by a terminal with dual connectivity to afirst and a second cell group. The method may comprise: receivingconfiguration information of PH (Power Headroom) corresponding to anactivated serving cell belonging to the second cell group; and in caseconditions for triggering PHR are satisfied, generating the PHR andtransmitting the generated PHR to a serving cell belonging to the firstcell group, wherein the PHR can be configured to include either ofvirtual PH information about an activated serving cell belonging to thesecond cell group based on configuration information of the received PHand actual PH information determined on the basis of schedulinginformation of the terminal.

At this time, the first cell group can be an MCG (Master Cell Group),and the second cell group can be an SCG (Secondary Cell Group).

Also, the conditions for triggering PHR can include the first PHRtriggering condition and the second triggering condition.

Also, the PHR can include the virtual PH information in case the PHR istriggered according to the first PHR condition.

Also, in case the PHR is configured to include the virtual PHinformation, the first PHR triggering condition can be ignored.

Also, in case the PHR is configured to include the virtual PHinformation, the second PHR triggering condition can be satisfied evenwhen a terminal has not secured uplink resources for new transmission.

According to the disclosure of the present specification, theaforementioned problem in the prior art can be solved. Morespecifically, according to the disclosure of the present specification,a terminal with dual connectivity can perform PHR transmissionefficiently by applying virtual PH information according to schedulingand PHR triggering conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system.

FIG. 2 illustrates a structure of a radio frame according to frequencydivision duplex (FDD) of 3rd generation partnership project (3GPP) longterm evolution (LTE).

FIG. 3 illustrates a structure of a downlink radio frame according totime division duplex (TDD) in 3GPP LTE.

FIG. 4 illustrates an example of a resource grid for one uplink ordownlink slot in 3GPP LTE.

FIG. 5 illustrates a structure of a downlink subframe.

FIG. 6 illustrates an example of resource mapping of a PDCCH.

FIG. 7 illustrates an example of monitoring of a PDCCH.

FIG. 8 illustrates the architecture of a UL sub-frame in 3GPP LTE.

FIG. 9 illustrates a subframe having an EPDCCH.

FIG. 10 illustrates an example of a PRB pair.

FIG. 11 illustrates a PUCCH and a PUSCH on an uplink subframe.

FIG. 12 illustrates an example of comparison between a single carriersystem and a carrier aggregation system.

FIG. 13 exemplifies cross-carrier scheduling in the carrier aggregationsystem.

FIG. 14 illustrates an example of scheduling performed whencross-carrier scheduling is configured in a cross-carrier scheduling.

FIG. 15 illustrates one example of an extended PHR MAC CE.

FIG. 16 is a flow diagram illustrating a PHR transmission methodaccording to one disclosure of the present specification.

FIG. 17 is a block diagram illustrating a wireless communication systemin which the disclosure of the present specification is implemented.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, based on 3rd Generation Partnership Project (3GPP) longterm evolution (LTE) or 3GPP LTE-advanced (LTE-A), the present inventionwill be applied. This is just an example, and the present invention maybe applied to various wireless communication systems. Hereinafter, LTEincludes LTE and/or LTE-A.

The technical terms used herein are used to merely describe specificembodiments and should not be construed as limiting the presentinvention. Further, the technical terms used herein should be, unlessdefined otherwise, interpreted as having meanings generally understoodby those skilled in the art but not too broadly or too narrowly.Further, the technical terms used herein, which are determined not toexactly represent the spirit of the invention, should be replaced by orunderstood by such technical terms as being able to be exactlyunderstood by those skilled in the art. Further, the general terms usedherein should be interpreted in the context as defined in thedictionary, but not in an excessively narrowed manner.

The expression of the singular number in the present invention includesthe meaning of the plural number unless the meaning of the singularnumber is definitely different from that of the plural number in thecontext. In the following description, the term ‘include’ or ‘have’ mayrepresent the existence of a feature, a number, a step, an operation, acomponent, a part or the combination thereof described in the presentinvention, and may not exclude the existence or addition of anotherfeature, another number, another step, another operation, anothercomponent, another part or the combination thereof.

The terms ‘first’ and ‘second’ are used for the purpose of explanationabout various components, and the components are not limited to theterms ‘first’ and ‘second’. The terms ‘first’ and ‘second’ are only usedto distinguish one component from another component. For example, afirst component may be named as a second component without deviatingfrom the scope of the present invention.

It will be understood that when an element or layer is referred to asbeing “connected to” or “coupled to” another element or layer, it can bedirectly connected or coupled to the other element or layer orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly connected to” or “directlycoupled to” another element or layer, there are no intervening elementsor layers present.

Hereinafter, exemplary embodiments of the present invention will bedescribed in greater detail with reference to the accompanying drawings.In describing the present invention, for ease of understanding, the samereference numerals are used to denote the same components throughout thedrawings, and repetitive description on the same components will beomitted. Detailed description on well-known arts which are determined tomake the gist of the invention unclear will be omitted. The accompanyingdrawings are provided to merely make the spirit of the invention readilyunderstood, but not should be intended to be limiting of the invention.It should be understood that the spirit of the invention may be expandedto its modifications, replacements or equivalents in addition to what isshown in the drawings.

As used herein, ‘base station’ generally refers to a fixed station thatcommunicates with a wireless device and may be denoted by other termssuch as eNB (evolved-NodeB), BTS (base transceiver system), or accesspoint.

As used herein, ‘user equipment (UE)’ may be stationary or mobile, andmay be denoted by other terms such as device, wireless device, terminal,MS (mobile station), UT (user terminal), SS (subscriber station), MT(mobile terminal) and etc.

FIG. 1 illustrates a wireless communication system.

As seen with reference to FIG. 1, the wireless communication systemincludes at least one base station (BS) 20. Each base station 20provides a communication service to specific geographical areas(generally, referred to as cells) 20 a, 20 b, and 20 c. The cell can befurther divided into a plurality of areas (sectors).

The UE generally belongs to one cell and the cell to which the UE belongis referred to as a serving cell. A base station that provides thecommunication service to the serving cell is referred to as a servingBS. Since the wireless communication system is a cellular system,another cell that neighbors to the serving cell is present. Another cellwhich neighbors to the serving cell is referred to a neighbor cell. Abase station that provides the communication service to the neighborcell is referred to as a neighbor BS. The serving cell and the neighborcell are relatively decided based on the UE.

Hereinafter, a downlink means communication from the base station 20 tothe UE1 10 and an uplink means communication from the UE 10 to the basestation 20. In the downlink, a transmitter may be a part of the basestation 20 and a receiver may be a part of the UE 10. In the uplink, thetransmitter may be a part of the UE 10 and the receiver may be a part ofthe base station 20.

Meanwhile, the wireless communication system may be generally dividedinto a frequency division duplex (FDD) type and a time division duplex(TDD) type. According to the FDD type, uplink transmission and downlinktransmission are achieved while occupying different frequency bands.According to the TDD type, the uplink transmission and the downlinktransmission are achieved at different time while occupying the samefrequency band. A channel response of the TDD type is substantiallyreciprocal. This means that a downlink channel response and an uplinkchannel response are approximately the same as each other in a givenfrequency area. Accordingly, in the TDD based wireless communicationsystem, the downlink channel response may be acquired from the uplinkchannel response. In the TDD type, since an entire frequency band istime-divided in the uplink transmission and the downlink transmission,the downlink transmission by the base station and the uplinktransmission by the terminal may not be performed simultaneously. In theTDD system in which the uplink transmission and the downlinktransmission are divided by the unit of a subframe, the uplinktransmission and the downlink transmission are performed in differentsubframes.

Hereinafter, the LTE system will be described in detail.

FIG. 2 illustrates a structure of a radio frame according to FDD of 3rdgeneration partnership project (3GPP) long term evolution (LTE).

The radio frame of FIG. 2 may be found in the section 5 of 3GPP TS36.211 V10.4.0 (2011-12) “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation (Release 10)”.

The radio frame includes 10 subframes indexed 0 to 9. One subframeincludes two consecutive slots. Accordingly, the radio frame includes 20slots. The time taken for one subframe to be transmitted is denoted TTI(transmission time interval). For example, the length of one subframemay be 1 ms, and the length of one slot may be 0.5 ms.

The structure of the radio frame is for exemplary purposes only, andthus the number of subframes included in the radio frame or the numberof slots included in the subframe may change variously.

Meanwhile, one slot may include a plurality of OFDM symbols. The numberof OFDM symbols included in one slot may vary depending on a cyclicprefix (CP).

FIG. 3 illustrates a structure of a downlink radio frame according toTDD in 3GPP LTE.

For this, 3GPP TS 36.211 V10.4.0 (2011-23) “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation(Release 8)”, Ch. 4 may be referenced, and this is for TDD (timedivision duplex).

Subframes having index #1 and index #6 are denoted special subframes,and include a DwPTS(Downlink Pilot Time Slot: DwPTS), a GP(Guard Period)and an UpPTS(Uplink Pilot Time Slot). The DwPTS is used for initial cellsearch, synchronization, or channel estimation in a terminal. The UpPTSis used for channel estimation in the base station and for establishinguplink transmission sync of the terminal. The GP is a period forremoving interference that arises on uplink due to a multi-path delay ofa downlink signal between uplink and downlink.

In TDD, a DL (downlink) subframe and a UL (Uplink) co-exist in one radioframe.

Table 1 shows an example of configuration of a radio frame.

TABLE 1 UL-DL Switch-point Subframe index configuration periodicity 0 12 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U 1  5 ms D S U U D D S U U D2  5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U UD D D D D D 5 10 ms D S U D D D D D D D 6  5 ms D S U U U D S U U D

‘D’ denotes a DL subframe, ‘U’ a UL subframe, and ‘S’ a specialsubframe. When receiving a UL-DL configuration from the base station,the terminal may be aware of whether a subframe is a DL subframe or a ULsubframe according to the configuration of the radio frame.

FIG. 4 illustrates an example of a resource grid for one uplink ordownlink slot in 3GPP LTE.

Referring to FIG. 4, the uplink slot includes a plurality of OFDM(orthogonal frequency division multiplexing) symbols in the time domainand NRB resource blocks (RBs) in the frequency domain. For example, inthe LTE system, the number of resource blocks (RBs), i.e., NRB, may beone from 6 to 110.

The resource block is a unit of resource allocation and includes aplurality of sub-carriers in the frequency domain. For example, if oneslot includes seven OFDM symbols in the time domain and the resourceblock includes 12 sub-carriers in the frequency domain, one resourceblock may include 7×12 resource elements (REs).

FIG. 5 illustrates a structure of a downlink subframe.

In FIG. 5, assuming the normal CP, one slot includes seven OFDM symbols,by way of example.

The DL (downlink) subframe is split into a control region and a dataregion in the time domain. The control region includes up to first threeOFDM symbols in the first slot of the subframe. However, the number ofOFDM symbols included in the control region may be changed. A PDCCH(physical downlink control channel) and other control channels areassigned to the control region, and a PDSCH is assigned to the dataregion.

The physical channels in 3GPP LTE may be classified into data channelssuch as PDSCH (physical downlink shared channel) and PUSCH (physicaluplink shared channel) and control channels such as PDCCH (physicaldownlink control channel), PCFICH (physical control format indicatorchannel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH(physical uplink control channel).

The PCFICH transmitted in the first OFDM symbol of the subframe carriesCIF (control format indicator) regarding the number (i.e., size of thecontrol region) of OFDM symbols used for transmission of controlchannels in the subframe. The wireless device first receives the CIF onthe PCFICH and then monitors the PDCCH.

Unlike the PDCCH, the PCFICH is transmitted through a fixed PCFICHresource in the subframe without using blind decoding.

The PHICH carries an ACK (positive-acknowledgement)/NACK(negative-acknowledgement) signal for a UL HARQ (hybrid automatic repeatrequest). The ACK/NACK signal for UL (uplink) data on the PUSCHtransmitted by the wireless device is sent on the PHICH.

The PBCH (physical broadcast channel) is transmitted in the first fourOFDM symbols in the second slot of the first subframe of the radioframe. The PBCH carries system information necessary for the wirelessdevice to communicate with the base station, and the system informationtransmitted through the PBCH is denoted MIB (master information block).In comparison, system information transmitted on the PDSCH indicated bythe PDCCH is denoted SIB (system information block).

The PDCCH may carry activation of VoIP (voice over internet protocol)and a set of transmission power control commands for individual UEs insome UE group, resource allocation of an higher layer control messagesuch as a random access response transmitted on the PDSCH, systeminformation on DL-SCH, paging information on PCH, resource allocationinformation of UL-SCH (uplink shared channel), and resource allocationand transmission format of DL-SCH (downlink-shared channel). A pluralityof PDCCHs may be sent in the control region, and the terminal maymonitor the plurality of PDCCHs. The PDCCH is transmitted on one CCE(control channel element) or aggregation of some consecutive CCEs. TheCCE is a logical allocation unit used for providing a coding rate perradio channel's state to the PDCCH. The CCE corresponds to a pluralityof resource element groups. Depending on the relationship between thenumber of CCEs and coding rates provided by the CCEs, the format of thePDCCH and the possible number of PDCCHs are determined.

The control information transmitted through the PDCCH is denoteddownlink control information (DCI). The DCI may include resourceallocation of PDSCH (this is also referred to as DL (downlink) grant),resource allocation of PUSCH (this is also referred to as UL (uplink)grant), a set of transmission power control commands for individual UEsin some UE group, and/or activation of VoIP (Voice over InternetProtocol).

The base station determines a PDCCH format according to the DCI to besent to the terminal and adds a CRC (cyclic redundancy check) to controlinformation. The CRC is masked with a unique identifier (RNTI; radionetwork temporary identifier) depending on the owner or purpose of thePDCCH. In case the PDCCH is for a specific terminal, the terminal'sunique identifier, such as C-RNTI (cell-RNTI), may be masked to the CRC.Or, if the PDCCH is for a paging message, a paging indicator, forexample, P-RNTI (paging-RNTI) may be masked to the CRC. If the PDCCH isfor a system information block (SIB), a system information identifier,SI-RNTI (system information-RNTI), may be masked to the CRC. In order toindicate a random access response that is a response to the terminal'stransmission of a random access preamble, an RA-RNTI (randomaccess-RNTI) may be masked to the CRC.

In 3GPP LTE, blind decoding is used for detecting a PDCCH. The blinddecoding is a scheme of identifying whether a PDCCH is its own controlchannel by demasking a desired identifier to the CRC (cyclic redundancycheck) of a received PDCCH (this is referred to as candidate PDCCH) andchecking a CRC error. The base station determines a PDCCH formataccording to the DCI to be sent to the wireless device, then adds a CRCto the DCI, and masks a unique identifier (this is referred to as RNTI(radio network temporary identifier) to the CRC depending on the owneror purpose of the PDCCH.

FIG. 6 illustrates an example of resource mapping of a PDCCH.

R0 denotes a reference signal of a 1st antenna, R1 denotes a referencesignal of a 2nd antenna, R2 denotes a reference signal of a 3rd antenna,and R3 denotes a reference signal of a 4th antenna.

A control region in a subframe includes a plurality of control channelelements (CCEs). The CCE is a logical allocation unit used to providethe PDCCH with a coding rate depending on a state of a radio channel,and corresponds to a plurality of resource element groups (REGs). TheREG includes a plurality of resource elements (REs). According to therelationship between the number of CCEs and the coding rate provided bythe CCEs, a PDCCH format and a possible PDCCH bit number are determined.

A BS determines the number of CCEs used in transmission of the PDCCHaccording to a channel state. For example, a UE having a good DL channelstate may use one CCE in PDCCH transmission. A UE having a poor DLchannel state may use 8 CCEs in PDCCH transmission.

One REG (indicated by a quadruplet in the drawing) includes 4 REs. OneCCE includes 9 REGs. The number of CCEs used to configure one PDCCH maybe selected from {1, 2, 4, 8}. Each element of {1, 2, 4, 8} is referredto as a CCE aggregation level.

A control channel consisting of one or more CCEs performs interleavingin unit of REG, and is mapped to a physical resource after performingcyclic shift based on a cell identifier (ID).

FIG. 7 illustrates an example of monitoring of a PDCCH.

A UE cannot know about a specific position in a control region in whichits PDCCH is transmitted and about a specific CCE aggregation or DCIformat used for transmission. A plurality of PDCCHs can be transmittedin one subframe, and thus the UE monitors the plurality of PDCCHs inevery subframe. Herein, monitoring is an operation of attempting PDCCHdecoding by the UE according to a PDCCH format.

The 3GPP LTE uses a search space to reduce an overhead of blinddecoding. The search space can also be called a monitoring set of a CCEfor the PDCCH. The UE monitors the PDCCH in the search space.

The search space is classified into a common search space and aUE-specific search space. The common search space is a space forsearching for a PDCCH having common control information and consists of16 CCEs indexed with 0 to 15. The common search space supports a PDCCHhaving a CCE aggregation level of {4, 8}. However, a PDCCH (e.g., DCIformats 0, 1A) for carrying UE-specific information can also betransmitted in the common search space. The UE-specific search spacesupports a PDCCH having a CCE aggregation level of {1, 2, 4, 8}.

Table 2 below shows the number of PDCCH candidates monitored by awireless device.

TABLE 2 Number M(L) Search space S(L) k of PDCCH Type Aggregation levelL Size [in CCEs] candidates UE- 1 6 6 specific 2 12 6 4 8 2 8 16 2Common 4 16 4 8 16 2

A size of the search space is determined by Table 2 above, and a startpoint of the search space is defined differently in the common searchspace and the UE-specific search space. Although a start point of thecommon search space is fixed irrespective of a subframe, a start pointof the UE-specific search space may vary in every subframe according toa UE identifier (e.g., C-RNTI), a CCE aggregation level, and/or a slotnumber in a radio frame. If the start point of the UE-specific searchspace exists in the common search space, the UE-specific search spaceand the common search space may overlap with each other.

In a CCE aggregation level Lε {1,2,3,4}, a search space S(L)k is definedas a set of PDCCH candidates. A CCE corresponding to a PDCCH candidate mof the search space S(L)k is given by Equation 1 below.L{(Y _(k) +m′)mod └N _(CCE,k) /L┘}+i  [Equation 2]

Herein, i=0, 1, . . . , L−1, m=0, . . . , M(L)−1, and NCCE,k denotes thetotal number of CCEs that can be used for PDCCH transmission in acontrol region of a subframe k. The control region includes a set ofCCEs numbered from 0 to NCCE,k−1. M(L) denotes the number of PDCCHcandidates in a CCE aggregation level L of a given search space.

If a carrier indicator field (CIF) is configured for the wirelessdevice, m′=m+M(L)ncif. Herein, ncif is a value of the CIF. If the CIF isnot configured for the wireless device, m′=m.

In a common search space, Yk is set to 0 with respect to two aggregationlevels L=4 and L=8.

In a UE-specific search space of the aggregation level L, a variable Ykis defined by Equation 2 below.Y _(k)=(A·Y _(k-1))mod D  [Equation 3]

Herein, Y−1=nRNT≠0, A=39827, D=65537, k=floor(ns/2), and ns denotes aslot number in a radio frame.

When the UE monitors the PDCCH by using the C-RNTI, a search space and aDCI format used in monitoring are determined according to a transmissionmode of the PDSCH.

Meanwhile, when the UE monitors the PDCCH by using the C-RNTI, a searchspace and a DCI format used in monitoring are determined according to atransmission mode (TM) of the PDSCH. Table 3 below shows an example ofPDCCH monitoring for which the C-RNTI is configured.

TABLE 3 Transmission Transmission mode of PDSCH mode DCI format Searchspace according to PDCCH Transmission DCI format 1A Public service andSingle antenna port, port 0 mode 1 terminal specific DCI format 1Terminal specific Single antenna port, port 0 Transmission DCI format 1APublic service and Transmit diversity mode 2 terminal specific DCIformat 1 Terminal specific Transmit diversity Transmission DCI format 1APublic service and Transmit diversity mode 3 terminal specific DCIformat 2A Terminal specific CDD(Cyclic Delay Diversity) or transmitdiversity Transmission DCI format 1A Public service and Transmitdiversity mode 4 terminal specific DCI format 2 Terminal specificClosed-loop spatial multiplexing Transmission DCI format 1A Publicservice and Transmit diversity mode 5 terminal specific DCI format 1DTerminal specific MU-MIMO(Multi-user Multiple Input Multiple Output)Transmission DCI format 1A Public service and Transmit diversity mode 6terminal specific DCI format 1B Terminal specific Closed-loop spatialmultiplexing Transmission DCI format 1A Public service and If the numberof PBCH transmisison mode 7 terminal specific ports is 1, single antennaport, port 0. Otherwise, transmit diversity DCI format 1 Terminalspecific Single antenna port, port 5 Transmission DCI format 1A Publicservice and If the number of PBCH transmisison mode 8 terminal specificports is 1, single antenna port, port 0. Otherwise, transmit diversityDCI format 2B Terminal specific Dual layer transmisison (port 7 or 8),or single antenna port, port 7 or 8 Transmission DCI format 1A Publicservice and Non-MBSFN sub-frame: if the mode 9 terminal specific numberof PBCH antenna ports is 1, port 0 is used as independent antenna port.Otherwise, transmit Diversity MBSFN sub-frame: port 7 as independentantenna port DCI format 2C Terminal specific 8 transmisison layers,ports 7-14 are used or port 7 or 8 is used as independent antenna portTransmission DCI 1A Public service and Non-MBSFN sub-frame: if the mode10 terminal specific number of PBCH antenna ports is 1, port 0 is usedas independent antenna port. Otherwise, transmit Diversity MBSFNsub-frame: port 7 as independent antenna port DCI format 2D Terminalspecific 8 transmisison layers, ports 7-14 are used or port 7 or 8 isused as independent antenna port

The usage of the DCI format is classified as shown in table below.

TABLE 4 DCI format Contents DCI format 0 Used in PUSCH scheduling DCIformat 1 Used in scheduling of one PDSCH codeword DCI format 1A Used incompact scheduling of one PDSCH codeword and random access process DCIformat 1B Used in compact scheduling of one PDSCH codeword havingprecoding information DCI format 1C Used in very compact scheduling ofone PDSCH codeword DCI format 1D Used in precoding and compactscheduling of one PDSCH codeword having power offset information DCIformat 2 Used in PDSCH scheduling of terminals configured in closed-loopspatial multiplexing mode DCI format 2A Used in PDSCH scheduling ofterminals configured in open-loop spatial multiplexing mode DCI format2B DCI format 2B is used for resouce allocation for dual-layerbeam-forming of PDSCH. DCI format 2C DCI format 2C is used for resouceallocation for closed-loop SU-MIMO or MU-MIMO operation to 8 layers. DCIformat 2D DCI format 2C is used for resouce allocation to 8 layers. DCIformat 3 Used to transmit TPC command of PUCCH and PUSCH having 2 bitpower adjustments DCI format 3A Used to transmit TPC command of PUCCHand PUSCH having 1 bit power adjustment DCI format 4 Used in PUSCHscheduling of uplink (UP) operated in multi-antenna port transmisisonmode

FIG. 8 illustrates the architecture of a UL sub-frame in 3GPP LTE.

Referring to FIG. 8, the uplink sub-frame may be separated into acontrol region and a data region in the frequency domain. The controlregion is allocated a PUCCH (physical uplink control channel) fortransmission of uplink control information. The data region is allocateda PUSCH (physical uplink shared channel) for transmission of data (insome cases, control information may also be transmitted).

The PUCCH for one user equipment is allocated in resource block (RB)pair in the sub-frame. The resource blocks in the resource block pairtake up different sub-carriers in each of the first and second slots.The frequency occupied by the resource blocks in the resource block pairallocated to the PUCCH is varied with respect to a slot boundary. Thisis referred to as the RB pair allocated to the PUCCH having beenfrequency-hopped at the slot boundary. A frequency diversity gain may beobtained by transmitting uplink control information through differentsub-carriers over time.

Since the UE transmits UL control information over time throughdifferent subcarriers, a frequency diversity gain can be obtained. Inthe figure, m is a location index indicating a logical frequency-domainlocation of the RB pair allocated to the PUCCH in the sub-frame.

Uplink control information transmitted on the PUCCH may include a HARQACK/NACK, a channel quality indicator (CQI) indicating the state of adownlink channel, a scheduling request (SR) which is an uplink radioresource allocation request, and the like.

The PUSCH is mapped to a uplink shared channel (UL-SCH), a transportchannel Uplink data transmitted on the PUSCH may be a transport block, adata block for the UL-SCH transmitted during the TTI. The transportblock may be user information. Or, the uplink data may be multiplexeddata. The multiplexed data may be data obtained by multiplexing thetransport block for the UL-SCH and control information. For example,control information multiplexed to data may include a CQI, a precodingmatrix indicator (PMI), an HARQ, a rank indicator (RI), or the like. Orthe uplink data may include only control information.

A carrier aggregation system is now described.

A carrier aggregation system aggregates a plurality of componentcarriers (CCs). A meaning of an existing cell is changed according tothe above carrier aggregation. According to the carrier aggregation, acell may signify a combination of a downlink component carrier and anuplink component carrier or an independent downlink component carrier.

Further, the cell in the carrier aggregation may be classified into aprimary cell, a secondary cell, and a serving cell. The primary cellsignifies a cell operated in a primary frequency. The primary cellsignifies a cell which UE performs an initial connection establishmentprocedure or a connection reestablishment procedure or a cell indicatedas a primary cell in a handover procedure. The secondary cell signifiesa cell operating in a secondary frequency. Once the RRC connection isestablished, the secondary cell is used to provided an additional radioresource.

As described above, the carrier aggregation system may support aplurality of component carriers (CCs), that is, a plurality of servingcells unlike a single carrier system.

The carrier aggregation system may support a cross-carrier scheduling.The cross-carrier scheduling is a scheduling method capable ofperforming resource allocation of a PDSCH transmitted through othercomponent carrier through a PDCCH transmitted through a specificcomponent carrier and/or resource allocation of a PUSCH transmittedthrough other component carrier different from a component carrierbasically linked with the specific component carrier.

Meanwhile, the PDCCH is monitored in an area restricted to the controlregion in the subframe, and a CRS transmitted in a full band is used todemodulate the PDCCH. As a type of control data is diversified and anamount of control data is increased, scheduling flexibility is decreasedwhen using only the existing PDCCH. In addition, in order to decrease anoverhead caused by CRS transmission, an enhanced PDCCH (EPDCCH) isintroduced.

FIG. 9 illustrates a subframe having an EPDCCH.

A subframe may include a zero or one PDCCH region 410 or zero or moreEPDCCH regions 420 and 430.

The EPDCCH regions 420 and 430 are regions in which a wireless devicemonitors an EPDCCH. The PDCCH region 410 is located in up to four frontOFDM symbols of a subframe, while the EPDCCH regions 420 and 430 mayflexibly be scheduled in OFDM symbols after the PDCCH region 410.

One or more EPDCCH regions 420 and 430 may be designated for thewireless device, and the wireless devices may monitor an EPDCCH in thedesignated EPDCCH regions 420 and 430.

The number/location/size of the EPDCCH regions 420 and 430 and/orinformation on a subframe for monitoring an EPDCCH may be provided by abase station to a wireless device through an RRC message or the like.

In the PDCCH region 410, a PDCCH may be demodulated based on a CRS. Inthe EPDCCH regions 420 and 430, a demodulation (DM) RS may be defined,instead of a CRS, for demodulation of an EPDCCH. An associated DM RS maybe transmitted in the corresponding EPDCCH regions 420 and 430.

An RS sequence rns(m) for the associated DM RS is represented byEquation 3.

$\begin{matrix}{{r_{l,{ns}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Here, m=0, 1, . . . , 2N_(maxRB)−1, N_(maxRB) denotes the maximum numberof RBs, ns denotes the number of a slot in a radio frame, and 1 denotesthe number of an OFDM symbol in a slot.

A pseudo-random sequence c(i) is defined by the following gold sequencewith a length of 31.

Here, m=0, 1, . . . , 12N_(RB)−1, and N_(RB) denotes the maximum numberof RBs. A pseudo-random sequence generator may be initialized asc_(init)=(floor(ns/2)+1)(2N_(EPDCCH,ID)+1)2¹⁶+n_(EPDCCH,SCID) in eachstarting subframe. ns is the number of a slot in a radio frame,N_(EPDCCH,ID) is a value associated with an EPDCCH set, which is giventhrough a higher-layer signal, and n_(EPDCCH,SCID) is a specific value.

The EPDCCH regions 420 and 430 may be used for scheduling for differentcells, respectively. For example, an EPDCCH in the EPDCCH region 420 maycarry scheduling information for a primary cell, and an EPDCCH in theEPDCCH region 430 may carry scheduling information for a secondary cell.

When EPDCCHs are transmitted in the EPDCCH regions 420 and 430 throughmultiple antennas, the same precoding as for the EPDCCHs may be appliedto DM RSs in the EPDCCH regions 420 and 430.

Comparing with a CCE used as a transmission resource unit for a PDCCH, atransmission resource unit for an EPDCCH is an enhanced control channelelement (ECCE). An aggregation level may be defined as a resource unitfor monitoring an EPDCCH. For example, defining one ECCE as a minimumresource for an EPDCCH, an aggregation level may be defined as L={1, 2,4, 8, 16}.

Hereinafter, an EPDCCH search space may correspond to an EPDCCH region.In an EPDCCH search space, one or more EPDCCH candidates may bemonitored by one or more aggregation levels.

Hereinafter, resource allocation for an EPDCCH will be described.

An EPDCCH is transmitted using one or more ECCEs. An ECCE includes aplurality of enhanced resource element groups (EREGs). An ECCE mayinclude four EREGs or eight EREGs according to a subframe type based ona TDD DL-UL configuration and a CP. For example, an ECCE may includefour EREGs in a normal CP, while an ECCE may include eight EREGs in anextended CP.

A physical resource block (PRB) pair refers to two PRBs having the sameRB number in one subframe. A PRB pair refers to a first PRB of a firstslot and a second PRB of a second slot in the same frequency domain. Ina normal CP, a PRB pair includes 12 subcarriers and 14 OFDM symbols andthus includes 168 REs.

FIG. 10 illustrates an example of a PRB pair.

Although it is shown below that a subframe includes two slots and a PRBpair in one slot includes seven OFDM symbols and 12 subcarriers, thesenumbers of OFDM symbols and subcarriers are provided for illustrativepurposes only.

In one subframe, a PRB pair includes 168 REs. 16 EREGs are formed from144 Res, excluding 24 REs for a DM RS. Thus, one EREG may include nineREs. Here, a CSI-RS or CRS may be disposed in one PRB pair in additionthe DM RM. In this case, the number of available REs may be reduced andthe number of REs included in one EREG may be reduced. The number of REsincluded in an EREG may change, while the number of EREGs included inone PRB pair, 16, does not change.

Here, as illustrated in FIG. 10, REs may sequentially be assignedindexes, starting from a top subcarrier in a leftmost OFDM symbol (1=0)(or REs may sequentially be assigned indexes in an upward direction,starting from a bottom subcarrier in the leftmost OFDM symbol (1=0)).Suppose that 16 EREGs are assigned indexes from 0 to 15. Here, nine REshaving RE index 0 are allocated to EREG 0. Likewise, nine REs having REindex k (k=0, . . . , 15) are allocated to EREG k.

A plurality of EREGs is combined to define an EREG group. For example,an EREG group including four EREGs may be defined as follows: EREG group#0={EREG 0, EREG 4, EREG 8, EREG 12}, EREG group #1={EREG 1, EREG 5,EREG 9, EREG 3}, EREG group #2={EREG 2, EREG 6, EREG 10, EREG 14}, andEREG group #3={EREG 3, EREG 7, EREG 11, EREG 15}. An EREG groupincluding eight EREGs may be defined as follows: EREG group #0={EREG 0,EREG 2, EREG 4, EREG 6, EREG 8, EREG 10, EREG 12, EREG 14} and EREGgroup #1={EREG 1, EREG 3, EREG 5, EREG 7, EREG 9, EREG 11, EREG 13, EREG15}.

As described above, an ECCE may include four EREGs, and an ECCE mayinclude eight EREGs in an extended CP. An ECCE is defined by an ERGEgroup. For example, FIG. 6 shows that ECCE #0 includes EREG group #0,ECCE #1 includes EREG group #1, ECCE #2 includes EREG group #2, and ECCE#3 includes EREG group #3.

There are localized transmission and distributed transmission inECCE-to-EREG mapping. In localized transmission, an EREG group formingone ECCE is selected from EREGs in one PRB pair. In distributedtransmission, an EREG group forming one ECCE is selected from EREGs indifferent PRB pairs.

FIG. 11 illustrates a PUCCH and a PUSCH on an uplink subframe.

Uplink control information (UCI) may be transmitted to the PUCCH. Inthis case, the PUCCH transmits various types of control informationaccording to a format. The UCI includes a HARQ ACK/NACK, a schedulingrequest (SR), and channel status information (CSI) representing adownlink channel status.

PUCCH format 1 transmits a scheduling request (SR). In this case, anon-off keying (OOK) scheme may be applied. PUCCH format 1a transmits anacknowledgement/non-acknowledgment (ACK/NACK) modulated by a binaryphase shift keying (BPS K) scheme with respect to one codeword. PUCCHformat 1b transmits an ACK/NACK modulated by a quadrature phase shiftkeying (QPSK) scheme with respect to two codewords. PUCCH format 2transmits a channel quality indicator (CQI) modulated by the QPSKscheme. PUCCH formats 2a and 2b transport the CQI and the ACK/NACK.

Table 5 illustrates the PUCCH formats.

TABLE 5 Format Description Format 1 Scheduling request (SR) Format 1aACK/NACK of 1 bit HARQ, Scheduling request (SR) may exist or not Format1b ACK/NACK of 2 bit HARQ, Scheduling request (SR) may exist or notFormat 2 CSI (20 code bits) Format 2 In the case of extended CP, CSI andHARQ ACK/NACK of 1 bit or 2 bits Format 2a CSI and HARQ ACK/NACK of 1bit Format 2b CSI and HARQ ACK/NACK of 2 bits Format 3 A plurality ofACK/NACKs for carrier aggregation

Each PUCCH format is mapped in the PUCCH to be transmitted. For example,the PUCCH formats 2/2a/2b are mapped in the resource block (m=0, 1 inFIG. 7) of a band edge allocated to the UE to be transmitted. A mixedPUCCH resource block (RB) may be mapped in a resource block (forexample, m=2) adjacent to the resource block to which the PUCCH formats2/2a/2b are allocated in a central direction of the band to betransmitted. The PUCCH formats 1/1a/1b to which the SR and the ACK/NACKare transmitted may be disposed in a resource block of m=4 or m=5. Thenumber N(2)RB of resource blocks which may be used in the PUCCH formats2/2a/2b to which the CQI is transmitted may be indicated to the UEthrough a broadcasted signal.

The aforementioned CSI is an index representing a status of the DLchannel, and may include at least one of a channel quality indicator(CQI) and a precoding matrix indicator (PMI). Further, a precoding typeindicator (PTI), a rank indication (RI), and the like may be included.

The CQI provides information on link adaptive parameters which may besupported by the UE for a predetermined time. The CQI may indicate adata rate which may be supported by the DL channel by considering acharacteristic of the UE receiver, a signal to interference plus noiseratio (SINR), and the like. The base station may determine modulation(QPSK, 16-QAM, 64-QAM, and the like) to be applied to the DL channel anda coding rate by using the CQI. The CQI may be generated by variousmethods. For example, the various methods include a method of quantizingand feed-backing the channel status as it is, a method of calculatingand feed-backing a signal to interference plus noise ratio (SINR), amethod of notifying a status which is actually applied to the channelsuch as a modulation coding scheme (MCS), and the like. When the CQI isgenerated based on the MCS, the MCS includes a modulation scheme, acoding scheme, and a coding rate according to the coding scheme, and thelike.

The PMI provides information on a precoding matrix in precoding based ona code book. The PMI is associated with the multiple input multipleoutput (MIMO). The feed-backing of the PMI in the MIMO may be called aclosed loop MIMO.

The RI is information on the number of layers recommended by the UE.That is, the RI represents the number of independent streams used inspatial multiplexing. The RI is fed-back only in the case where the UEoperates in an MIMO mode using the spatial multiplexing. The RI isalways associated with one or more CQI feed-backs. That is, the fed-backCQI is calculated by assuming a predetermined RI value. Since the rankof the channel is generally changed slower than the CQI, the RI isfed-back less than the number of CQIs. A transmission period of the RImay be a multiple of the CQI/PMI transmission period. The RI is definedin the entire system band, and a frequency-selective RI feedback is notsupported.

As such, the PUCCH is used only in the transmission of the UCI. To thisend, the PUCCH support multiple formats. A PUCCH having different bitnumbers for each subframe may be used according to a modulation schemesubordinate to the PUCCH format.

Meanwhile, the illustrated PUSCH is mapped in an uplink shared channel(UL-SCH) which is a transmission channel Uplink data transmitted on thePUSCH may be a transmission block which is a data block for the UL-SCHtransmitted during the TTI. The transmission block may include userdata. Alternatively, the uplink data may be multiplexed data. Themultiplexed data may be acquired by multiplexing the transmission blockfor the UL-SCH and the channel status information. For example, thechannel status information (CSI) multiplexed in the data may include theCQI, the PMI, the RI, and the like. Alternatively, the uplink data maybe constituted by only the uplink status information. Periodic oraperiodic channel status information may be transmitted through thePUSCH.

The PUSCH is allocated by the UL grant on the PDCCH. Although notillustrated, a fourth OFDM symbol of each slot of the normal CP is usedin the transmission of a demodulation reference signal (DM RS) for thePUSCH.

A carrier aggregation system is now described.

FIG. 12 illustrates an example of comparison between a single carriersystem and a carrier aggregation system.

Referring to FIG. 12, there may be various carrier bandwidths, and onecarrier is assigned to the terminal. On the contrary, in the carrieraggregation (CA) system, a plurality of component carriers (DL CC A toC, UL CC A to C) may be assigned to the terminal. Component carrier (CC)means the carrier used in then carrier aggregation system and may bebriefly referred as carrier. For example, three 20 MHz componentcarriers may be assigned so as to allocate a 60 MHz bandwidth to theterminal.

Carrier aggregation systems may be classified into a contiguous carrieraggregation system in which aggregated carriers are contiguous and anon-contiguous carrier aggregation system in which aggregated carriersare spaced apart from each other. Hereinafter, when simply referring toa carrier aggregation system, it should be understood as including boththe case where the component carrier is contiguous and the case wherethe control channel is non-contiguous.

When one or more component carriers are aggregated, the componentcarriers may use the bandwidth adopted in the existing system forbackward compatibility with the existing system. For example, the 3GPPLTE system supports bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHzand 20 MHz, and the 3GPP LTE-A system may configure a broad band of 20MHz or more only using the bandwidths of the 3GPP LTE system. Or, ratherthan using the bandwidths of the existing system, new bandwidths may bedefined to configure a wide band.

The system frequency band of a wireless communication system isseparated into a plurality of carrier frequencies. Here, the carrierfrequency means the cell frequency of a cell. Hereinafter, the cell maymean a downlink frequency resource and an uplink frequency resource. Or,the cell may refer to a combination of a downlink frequency resource andan optional uplink frequency resource. Further, in the general casewhere carrier aggregation (CA) is not in consideration, one cell mayalways have a pair of an uplink frequency resource and a downlinkfrequency resource.

In order for packet data to be transmitted/received through a specificcell, the terminal should first complete a configuration on the specificcell. Here, the configuration means that reception of system informationnecessary for data transmission/reception on a cell is complete. Forexample, the configuration may include an overall process of receivingcommon physical layer parameters or MAC (media access control) layersnecessary for data transmission and reception or parameters necessaryfor a specific operation in the RRC layer. A configuration-complete cellis in the state where, once when receiving information indicating packetdata may be transmitted, packet transmission and reception may beimmediately possible.

The cell that is in the configuration complete state may be left in anactivation or deactivation state. Here, the “activation” means that datatransmission or reception is being conducted or is in ready state. Theterminal may monitor or receive a control channel (PDCCH) and a datachannel (PDSCH) of the activated cell in order to identify resources(possibly frequency or time) assigned thereto.

The “deactivation” means that transmission or reception of traffic datais impossible while measurement or transmission/reception of minimalinformation is possible. The terminal may receive system information(SI) necessary for receiving packets from the deactivated cell. Incontrast, the terminal does not monitor or receive a control channel(PDCCH) and data channel (PDSCH) of the deactivated cell in order toidentify resources (probably frequency or time) assigned thereto.

Cells may be classified into primary cells and secondary cells, servingcells.

The primary cell means a cell operating at a primary frequency. Theprimary cell is a cell where the terminal conducts an initial connectionestablishment procedure or connection re-establishment procedure withthe base station or is a cell designated as a primary cell during thecourse of handover.

The secondary cell means a cell operating at a secondary frequency. Thesecondary cell is configured once an RRC connection is established andis used to provide an additional radio resource.

The serving cell is configured as a primary cell in case no carrieraggregation is configured or when the terminal cannot offer carrieraggregation. In case carrier aggregation is configured, the term“serving cell” denotes a cell configured to the terminal and a pluralityof serving cells may be included. One serving cell may consist of onedownlink component carrier or a pair of {downlink component carrier,uplink component carrier}. A plurality of serving cells may consist of aprimary cell and one or more of all the secondary cells.

The PCC (primary component carrier) means a component carrier (CC)corresponding to the primary cell. The PCC is, among several CCs, theone where the terminal initially achieves connection or RRC connectionwith the base station. The PCC is a special CC that is in charge ofconnection or RRC connection for signaling regarding multiple CCs andmanages terminal context information (UE context) that is connectioninformation related with the terminal. Further, the PCC achievesconnection with the terminal, so that the PCC is always left in theactivation state when in RRC connected mode. The downlink componentcarrier corresponding to the primary cell is denoted downlink primarycomponent carrier (DL PCC) and the uplink component carriercorresponding to the primary cell is denoted uplink primary componentcarrier (UL PCC).

The SCC (secondary component carrier) means a CC corresponding to asecondary cell. That is, the SCC is a CC other than the PCC, which isassigned to the terminal and is an extended carrier for the terminal toperform additional resource allocation in addition to the PCC. The SCCmay be left in activation state or deactivation state. The downlinkcomponent carrier corresponding to the secondary cell is denoteddownlink secondary component carrier (DL SCC) and the uplink componentcarrier corresponding to the secondary cell is denoted uplink secondarycomponent carrier (UL SCC).

The primary cell and the secondary cell have the followingcharacteristics.

First, the primary cell is used for transmitting a PUCCH. Second, theprimary cell is always left activated while the secondary cell may beactivated/deactivated depending on a specific condition. Third, when theprimary cell experiences a radio link failure (hereinafter, ‘RLF’), RRCre-connection is triggered. Fourth, the primary cell may be varied by ahandover procedure that comes with an RACH (random access channel)procedure or by altering a security key. Fifth, NAS (non-access stratum)information is received through the primary cell. Sixth, in the FDDsystem, the primary cell has always a pair of a DL PCC and a UL PCC.Seventh, a different component carrier (CC) may be set as a primary cellin each terminal. Eighth, the primary cell may be replaced only througha handover or cell selection/cell re-selection procedure. In adding anew serving cell, RRC signaling may be used to transmit systeminformation of a dedicated serving cell.

When configuring a serving cell, a downlink component carrier may formone serving cell or a downlink component carrier and an uplink componentcarrier form a connection to thereby configure one serving cell.However, a serving cell is not configured with one uplink componentcarrier alone.

Activation/deactivation of a component carrier is equivalent in conceptto activation/deactivation of a serving cell. For example, assuming thatserving cell 1 is constituted of DL CC1, activation of serving cell 1means activation of DL CC1. If serving cell2 is configured by connectionof DL CC2 and UL CC2, activation of serving cell2 means activation of DLCC2 and UL CC2. In this sense, each component carrier may correspond toa serving cell.

The number of component carriers aggregated between uplink and downlinkmay vary. When the number of downlink CCs is the same as the number ofuplink CCs is denoted symmetric aggregation, and when the numbers differfrom each other is denoted asymmetric aggregation. Further, the sizes(i.e., bandwidth) of CCs may be different from each other. For example,when five CCs are used to configure a 70 MHz band, the configuration maybe made as follows: 5 MHz CC(carrier #0)+20 MHz CC(carrier #1)+20 MHzCC(carrier #2)+20 MHz CC(carrier #3)+5 MHz CC(carrier #4).

As described above, the carrier aggregation system, unlike the singlecarrier system, may support a plurality of component carriers (CCs),i.e., a plurality of serving cells.

Such carrier aggregation system may support cross-carrier scheduling.The cross-carrier scheduling is a scheduling scheme that may conductresource allocation of a PUSCH transmitted through other componentcarriers than the component carrier basically linked to a specificcomponent carrier and/or resource allocation of a PDSCH transmittedthrough other component carriers through a PDCCH transmitted through thespecific component carrier. In other words, the PDCCH and the PDSCH maybe transmitted through different downlink CCs, and the PUSCH may betransmitted through an uplink CC other than the uplink CC linked to thedownlink CC where the PDCCH including a UL grant is transmitted. Assuch, the system supporting cross-carrier scheduling needs a carrierindicator indicating a DL CC/UL CC through which a PDSCH/PUSCH istransmitted where the PDCCH offers control information. The fieldincluding such carrier indicator is hereinafter denoted carrierindication field (CIF).

The carrier aggregation system supporting cross-carrier scheduling maycontain a carrier indication field (CIF) in the conventional DCI(downlink control information) format. In the cross-carrierscheduling-supportive carrier aggregation system, for example, an LTE-Asystem, may have 3 bits expanded due to addition of the CIF to theexisting DCI format (i.e., the DCI format used in the LTE system), andthe PDCCH architecture may reuse the existing coding method or resourceallocation method (i.e., CCE-based resource mapping).

FIG. 13 exemplifies cross-carrier scheduling in the carrier aggregationsystem.

Referring to FIG. 13, the base station may configure a PDCCH monitoringDL CC (monitoring CC) set. The PDCCH monitoring DL CC set consists ofsome of all of the aggregated DL CCs, and if cross-carrier scheduling isconfigured, the user equipment performs PDCCH monitoring/decoding onlyon the DL CCs included in the PDCCH monitoring DL CC set. In otherwords, the base station transmits a PDCCH for PDSCH/PUSCH that issubject to scheduling only through the DL CCs included in the PDCCHmonitoring DL CC set. The PDCCH monitoring DL CC set may be configuredUE-specifically, UE group-specifically, or cell-specifically.

FIG. 13 illustrates an example in which three DL CCs (DL CC A, DL CC B,and DL CC C) are aggregated, and DL CC A is set as a PDCCH monitoring DLCC. The user equipment may receive a DL grant for the PDSCH of DL CC A,DL CC B, and DL CC C through the PDCCH of DL CC A. The DCI transmittedthrough the PDCCH of DL CC A contains a CIF so that it may indicatewhich DL CC the DCI is for.

FIG. 14 illustrates an example of scheduling performed whencross-carrier scheduling is configured in a cross-carrier scheduling.

Referring to FIG. 14, DL CC 0, DL CC 2, and DL CC 4 belong to a PDCCHmonitoring DL CC set. The user equipment searches for DL grants/ULgrants for DL CC 0 and UL CC 0 (UL CC linked to DL CC 0 via SIB 2) inthe CSS of DL CC 0. The user equipment searches for DL grants/UL grantsfor DL CC 1 and UL CC 1 in SS 1 of DL CC 0. SS 1 is an example of USS.That is, SS 1 of DL CC 0 is a space for searching for a DL grant/ULgrant performing cross-carrier scheduling.

In what follows, Power Headroom (PH) will be described.

PH refers to extra power that can be used in addition to the power beingused currently for a terminal to perform uplink transmission. Forexample, suppose the maximum transmission power allowed for a terminalto perform uplink transmission is 10 W, and the terminal is consuming 9W within a frequency band of 10 MHz. Then since additional power of 1 Wis available for the terminal, PH becomes 1 W.

At this time, if a base station allocates a frequency band of 20 MHz tothe terminal, 18 W (=9 W×2) is needed. However, since the maximum powerof the terminal is 10 W, if 20 MHz is allocated to the terminal, theterminal may either be unable to use the whole frequency band or thebase station may not be able to receive a signal of the terminalproperly due to lack of power. To remedy the aforementioned problem, theterminal can report to the base station that PH is 1 W, by which thebase station can perform scheduling within the PH allowed. The reportperformed as described above is called Power Headroom Report (PHR).

Through a PHR procedure, a terminal can transmit the followinginformation to a serving base station: 1) information about a differencebetween the maximum transmission power and estimated UL-SCH (PUSCH)transmission power of a nominal terminal for each activated servingcell, 2) information about a difference between the maximum transmissionpower allowed for a terminal in a primary serving cell and estimatedPUCCH transmission power, or 3) information about a difference betweenthe maximum transmission power allowed in the primary serving cell,estimated UL-SCH, and PUCCH transmission power.

A terminal can have two types of PHR (type 1 and type 2). PH of anarbitrary terminal can be defined for a subframe i with respect to aserving cell c.

1. Type 1 of Power Headroom Report (PHR) (Type 1 PH)

Type 1 PH includes: 1) a case in which a terminal transmits a PUSCHwithout involving a PUCCH, 2) a case in which a terminal transmits aPUCCH and a PUSCH simultaneously, and 3) a case in which a PUSCH is notemployed for transmission.

First, in case a terminal transmits a PUSCH without involving a PUCCHfor a subframe i with respect to a serving cell c, the power headroomfor type 1 report can be expressed by the following mathematicalequation.PH _(type1,c)(i)=P _(CMAX,c)(i)−{10 log₁₀(M _(PUSCH,c)(i))+P _(O)_(PUSCH,c) (j)+α_(c)(j)·PL _(c)+Δ_(TF,c)(i)+f _(c)(i)}[dB],  [Equation5]

where P_(CMAX,c)(i) represents a terminal's maximum transmission powerwith respect to a serving cell c, and {circumflex over (P)}_(CMAX,c)(i)represents the maximum transmission power converted into a decibel value[dB].

In the mathematical equation above, P_(CMAX,c)(i) is the maximumtransmission power of a terminal obtained by applying offset values setby the network according to the maximum transmission power obtained bythe smaller of P_(EMAX) value determined on the basis of P-max valuetransmitted to a terminal by a base station through RRC signaling andP_(PowerClass) value determined according to transmission power classdetermined by the hardware level of each terminal. At this time, theoffset values can be the maximum power reduction (MPR) value, additionalmaximum power reduction (A-MPR) value, or power management maximum powerreduction (P-MPR) value; and can optionally be an offset value (ΔT_(C))applied according to a frequency band highly influenced by filtercharacteristics within a transmission unit of a terminal.

Different from P_(CMAX)(i), the P_(CMAX,c)(i) is the value applied onlyfor a serving cell c. Accordingly, the P-max value is obtained as thevalue P_(EMAX,c) applied only for the serving cell c, and each of theoffset values is also obtained by the value applied only for the servingcell c. In other words, those values are obtained as MPR_(c), A—MPR_(c),P—MPR_(c), and ΔT_(C,c). However, the P_(PowerClass) value is calculatedby using the same value as used for calculation for each terminal.

Also, M_(PUSCH,c)(i) represents the bandwidth of resources to which aPUSCH is allocated in a subframe i with respect to a serving cell c,expressed in terms of the number of RBs.

Also, P₀ _(PUSCH,C) (j) is the sum of

P_(0_(NOMINAL_(PUSCH), c))(j)and P₀ _(_) _(UE) _(_) _(PUSCH,c)(j) with respect to a serving cell c,and the index j in the higher layer is 0 or 1. In the case ofsemi-persistent grant PUSCH transmission (or re-transmission), j is 0while, in the case of dynamically scheduled grant) PUSCH transmission(or re-transmission), j is 2. Also, in the case of random accessresponse grant PUSCH transmission (or re-transmission), j is 2. Also, inthe case of random access response grant PUSCH transmission (orre-transmission), P₀ _(_) _(UE) _(_) _(PUSCH,c)(2) is 0, and P₀ _(_)_(NOMINAL) _(_) _(PUSCH,c)(2) is the sum of P₀ _(_) _(PRE) andΔ_(PREAMBLE) _(_) _(Msg3). At this time, the parameter P₀ _(_)_(PRE)(preambleInitialReceivedTargetPower) and Δ_(PREAMBLE-Msg3) issignaled from the higher layer.

If j is 0 or 1, a 3-bit parameter provided by the higher layer can beused to select one of α_(c) ε{0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1}values. In case j is 2, α_(c) (j) is always 1.

PL_(c) is an estimated value of downlink path loss (PL) with respect toa serving cell c calculated by a terminal, expressed in dBs, and can beobtained from “referenceSignalPower—higher layer filtered RSRP”. At thistime, referenceSignalPower is the value provided by the higher layer,which is the EPRE (Energy Per Resource Element) value of a downlinkreference signal, expressed in units of dBm. RSRP (Reference SignalReceived Power) is a received power value of a reference signal withrespect to a reference serving cell. pathlossReferenceLinking, a higherlayer parameter, is used to determine a serving cell selected as areference serving cell, referenceSignalPower used for calculation of thePL_(C), and higher layer filtered RSRP. At this time, the referenceserving cell configured by the pathlossReferenceLinking can be a primaryserving cell or a DL SCC of the corresponding secondary serving cellconfigured for an SIB2 connection with a UL CC.

Also, ΔTF,c(i) is a parameter for reflecting the effect caused by theMCS (Modulation Coding Scheme), which has a value of 10log₁₀((2^(BPRE·K) ^(s) −1)·β_(offset) ^(PUSCH)). At this time, K_(S) isa deltaMCS-Enabled parameter provided by the higher layer with respectto each serving cell c, which has the value of 1.25 or 0. In particular,in the case of transmission mode 2 for transmit diversity, K_(S) isalways 0. Also, in case only control information is transmitted throughPUSCH without UL-SCH data, BPRE=O_(CQI)/N_(RE), and for other cases,

${{BPRE} = {\sum\limits_{r = 0}^{C - 1}\;{K_{r}/N_{RE}}}},$where C is the number of code blocks, K_(r) represents the size of acode block, O_(CQI) represents the number of CQI/PMI bits including thenumber of CRC bits, and N_(RE) represents the number of determinedresource elements (namely, N_(RE)=M_(sc) ^(PUSCH-initial)·N_(symb)^(PUSCH-initial)). Also, in case only the control information istransmitted through PUSCH without UL-SCH data, β_(offset)^(PUSCH)=β_(offset) ^(CQI), and for other cases, β_(offset) ^(PUSCH)always set to 1.

Also, δ_(PUSCH,c) is a correction value and is determined according to aTPC command specified in the DCI format 0 or DCI format 4 with respectto a serving cell c or a TPC command within the DCI format 3/3Atransmitted being encoded together with other terminals. In the DCIformat 3/3A, CRC parity bits are scrambled with TPC-PUSCH-RNTI;therefore, only those terminals to which the RNTI value is allocated canrecognize the DCI format 3/3A. At this time, in case a terminal belongsto a plurality of serving cells, different RNTI values can be allocatedto the respective serving cells for identification of the serving cells.At this time, the adjustment condition of PUSCH power control withrespect to a current serving cell c is described by f_(c)(i), and incase accumulation is activated by the higher layer with respect to aserving cell c or in case PDCCH includes the DCI format 0 in which theTPC command δ_(PUSCH,c) is scrambled by a temporary-C-RNTI,“f_(c)(i)=f_(c)(i−1)+δ_(PUSCH,c)(i−K_(PUSCH))”. At this time,δ_(PUSCH,c)(i−K_(PUSCH)) is a TPC command belonging to the DCI format0/4 or 3/3A within the PDCCH transmitted through the (i−K_(PUSCH))-thsubframe, and MO) is the first value after accumulation reset. Also,K_(PUSCH) value is 4 in the case of FDD. In the presence of PDCCHscheduling PUSCH transmission through the subframe 2 or 7 when TDD UL/DLconfiguration is 0, if the LSB (Least Significant Bit) of UL indexwithin the DCI format 0/4 within the PDCCH is set to 1, K_(PUSCH) is 7.

Second, if a terminal transmits PUCCH and PUSCH simultaneously throughsubframe i with respect to a serving cell c, type 1 PH is expressed bythe following mathematical equation.PH _(type1,c)(i)={tilde over (P)} _(CMAX,c)(i)−{10 log₁₀(M_(PuscH,c)(i))+P _(O) _(_) _(PUSCH,c)(j)+α_(c)(j)·PL _(c)+Δ_(TF,c)(i)+f_(c)(i)}[dB]  [Equation 6]

where {tilde over (P)}_(CMAX,c)(i) is calculated under the assumptionthat the subframe i performs PUSCH transmission only. In this case, thephysical layer delivers {tilde over (P)}_(CMAX,c)(i) to the higher layerinstead of delivering P_(CMAX,c)(i).

Third, in case a terminal does not transmit PUSCH through the subframe iwith respect to a serving cell c, type 1 PH can be expressed as follows.PH _(type1,c)(i)={tilde over (P)} _(CMAX,c)(i)−{P _(O) _(_)_(PUSCH,c)(1)+α_(c)(1)·PL _(c) +f _(c)(i)}[dB]  [Equation 7]

where {tilde over (P)}_(CMAX,c)(i) is calculated under the assumptionthat MPR is 0 dB, A-MPR is 0 dB, P-MPR is 0 dB, and ΔT_(C) is 0 dB.

2. Type 2 of Power Headroom Report (PHR) (Type 2 PH)

Type 2 PH includes: 1) a case in which a terminal transmits PUCCH andPUSCH simultaneously through a subframe i with respect to a primaryserving cell, 2) a case in which a terminal transmits a PUCCH withoutPUSCH, and 3) a case in which PUCCH or PUSCH is not transmitted.

First, in case a terminal transmits PUCCH and PUSCH simultaneouslythrough the subframe i with respect to a primary serving cell, type 2 PHis calculated by the following mathematical equation.

$\begin{matrix}{{{PH}_{{type}\mspace{11mu} 2}(i)} = {{P_{{CMAX},c}(i)} - {\quad{\quad{10{{\log_{10}\left( \begin{matrix}{10^{{({{10{\log_{10}{({M_{{PUSCH},c}{(i)}})}}} + {P_{{O\_{PUSCH}},c}{(j)}} + {{\alpha_{c}{(j)}} \cdot {PL}_{c}} + {\Delta_{{TF},c}{(i)}} + {f_{c}{(i)}}})}/10} +} \\10^{{({P_{0{\_{PUCCH}}} + {PL}_{c} + {h{({n_{CQI},n_{HARQ},n_{SR}})}} + {\Delta_{F\_{PUCCH}}{(F)}} + {\Delta_{TxD}{(F^{\prime})}} + {g{(i)}}})}/10}\end{matrix} \right)}\lbrack{dB}\rbrack}}}}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

where Δ_(F) _(PUCCH) (F) is defined in the higher layer (RRC), and eachΔ_(F) _(PUCCH) (F) value coincides with the PUCCH format (F) related tothe PUCCH format 1a. Each PUCCH format (F) is described in the tablebelow.

TABLE 6 Number of bits PUCCH format Modulation scheme per subframe,M_(bit) 1 N/A N/A 1a BPSK  1 1b QPSK  2 2 QPSK 20 2a QPSK + BPSK 21 2bQPSK + QPSK 22 3 QPSK 48

If a terminal is set up by the higher layer to comprise two antennaports for PUCCH transmission, the higher layer provides Δ_(TxD)(F′)value for each PUCCH format F′. Otherwise, Δ_(TxD(F′)) is always 0.

Also, h(nCQI, nHARQ, nSR) has a different value for each PUCCH format.At this time, nCQI represents the number of bits of CQI (Channel QualityInformation). If SR (Scheduling Request) is configured for the subframei, and a transmission block related to UL-SCH of the terminal does notconfigured to handle SR, nSR=1, but nSR=0, otherwise. If the terminalbelongs to one serving cell, nHARQ represents the number of HARQ-ACKbits transmitted from the subframe i. In the case of PUCCH format1/1a/1b, h(nCQI, nHARQ, nSR)=0. In the case of PUCCH format 1b forchannel selection, if a terminal is configured for more than one servingcell, h(nCQI, nHARQ, nSR)=(nHARQ-1)/2, and h(nCQI, nHARQ, nSR)=0 forother cases. For the case of PUCCH format 2/2a/2b and normal cyclicprefix, if nCQI is larger than or equal to 4, h(nCQI, nHARQ, nSR)=10 log10(nCQI/4), and h(nCQI, nHARQ, nSR)=0, otherwise. For the case of PUCCHformat 2 and extended cyclic prefix, if “nCQI+nHARQ” is larger than orequal to 4, h(nCQI, nHARQ, nSR)=10 log 10((nCQI+nHARQ)/4), and h(nCQI,nHARQ, nSR)=0 otherwise. For the case of PUCCH format 3, if a terminalis configured to transmit PUCCH through 2 antenna ports by the higherlayer, or the terminal is configured to transmit 11 bits of HARQ-ACK/SR,h(nCQI, nHARQ, nSR)=(nHARQ+nSR−1)/3, and h(nCQI, nHARQ,nSR)=(nHARQ+nSR−1)/2 otherwise. P_(O) _(PUCCH) is a parameter formed bythe sum of P_(O) _(_) _(NOMINAL) _(_) _(PUCCH) parameter and P_(O) _(_)_(UE) _(_) _(PUCCH) p arameter provided by the higher layer.

Second, if a terminal transmits PUSCH without PUCCH through the subframei with respect to a primary serving cell, type 2 PH is calculated by thefollowing mathematical equation.

$\begin{matrix}{{{PH}_{{type}\mspace{11mu} 2}(i)} = {{P_{{CMAX},c}(i)} - {\quad{10{{\log_{10}\left( \begin{matrix}{10^{{({{10{\log_{10}{({M_{{PUSCH},c}{(i)}})}}} + {P_{{O\_{PUSCH}},c}{(j)}} + {{\alpha_{c}{(j)}} \cdot {PL}_{c}} + {\Delta_{{TF},c}{(i)}} + {f_{c}{(i)}}})}/10} +} \\10^{{({P_{0{\_{PUCCH}}} + {PL}_{c} + {g{(i)}}})}/10}\end{matrix} \right)}\lbrack{dB}\rbrack}}}}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

Third, if a terminal transmits PUCCH without PUSCH through the subframei with respect to a primary serving cell, type 2 PH is calculated by thefollowing mathematical equation.

$\begin{matrix}{{{PH}_{{type}\mspace{11mu} 2}(i)} = {{P_{{CMAX},c}(i)} - {10{{\log_{10}\begin{pmatrix}{10^{{({{P_{{O\_{PUSCH}},c}{(1)}} + {{\alpha_{c}{(1)}} \cdot {PL}_{c}} + {f_{c}{(i)}}})}/10} +} \\10^{{({P_{0{\_{PUCCH}}} + {PL}_{c} + {h{({n_{CQI},n_{HARQ},n_{SR}})}} + {\Delta_{F\_{PUCCH}}{(F)}} + {\Delta_{TxD}{(F^{\prime})}} + {g{(i)}}})}/10}\end{pmatrix}}\lbrack{dB}\rbrack}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Fourth, {tilde over (P)}_(CMAX,c)(i) is calculated under the assumptionthat MPR is 0 dB, A-MPR is 0 dB, P-MPR is 0 dB, and ΔT_(C)=0 dB.

$\begin{matrix}{{{PH}_{{type}\; 2}(i)} = {{{\overset{\sim}{P}}_{{CMAX},c}(i)} - {10{{\log_{10}\begin{pmatrix}{10^{{({{P_{{O\_{PUSCH}},c}{(1)}} + {{\alpha_{c}{(1)}} \cdot {PL}_{c}} + {f_{c}{(i)}}})}/10} +} \\10^{{({P_{0{\_{PUCCH}}} + {PL}_{c} + {g{(i)}}})}/10}\end{pmatrix}}\lbrack{dB}\rbrack}}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

where {tilde over (P)}_(CMAX,c)(i) is calculated under the assumptionthat MPR is 0 dB, A-MPR is 0 dB, P-MPR is 0 dB, and ΔT_(C) is 0 dB.

PH value is given in units of dB and has to be determined throughrounding-off to the nearest value within a range of 40 dB to −23 dB. Thedetermined PH value is delivered from the physical layer to the higherlayer.

Meanwhile, a reported PH value corresponds to the value estimated byusing one subframe.

If a terminal is not configured for extended PHR, only type 1 PH valueabout a primary serving cell is reported. On the other hand, if aterminal is configured for extended PHR, type 1 PH value and type 2 PHvalue are reported for each of activated serving cells to which uplinkis established. In what follows, extended PHR will be described indetail.

PH reporting delay refers to the difference between the start time of aPH reference interval and the start time at which a terminal beginstransmitting PH values through a wireless interface. Ideally, PHreporting delay has to be 0 ms, and PH reporting delay can be applied toall of the triggering methods configured for PHR.

The table below illustrates mapping of power headroom being reported.

TABLE 7 Measured quantity Reported value value (dB) POWER_HEADROOM_0 −23 ≦ PH <− 22 POWER_HEADROOM_1  −22 ≦ PH <− 21 POWER_HEADROOM_2  −21 ≦PH <− 20 POWER_HEADROOM_3  −20 ≦ PH <− 19 POWER_HEADROOM_4  −19 ≦ PH <−18 POWER_HEADROOM_5  −18 ≦ PH <− 17 . . . . . . POWER_HEADROOM_57 34 ≦PH < 35 POWER_HEADROOM_58 35 ≦ PH < 36 POWER_HEADROOM_59 36 ≦ PH < 37POWER_HEADROOM_60 37 ≦ PH < 38 POWER_HEADROOM_61 38 ≦ PH < 39POWER_HEADROOM_62 39 ≦ PH < 40 POWER_HEADROOM_63 PH ≧ 40

With reference to Table 7, PH value falls within the range from −23 dBto +40 dB. If 6 bits are used for the PH value, 64(=2⁶) indices can beexpressed; therefore, PH can be specified by a total of 64 levels. Asone example, if the bit value for PH is “0” (which is “000000” insix-bit expression), it indicates that PH level is “−23≦P_(PH)≦−22 dB”.

Meanwhile, control of PHR can be implemented through a periodic PHRtimer and a prohibitPHR-Timer. By transmitting the “dl-PathlossChange”value through an RRC message, a terminal controls triggering of PHR dueto change of path loss measured for downlink and change of P-MPR due topower management.

PHR can be triggered when at least one of the events below occurs.

1. In case path loss (for example, a path loss estimated by theterminal) is increased much more in at least one activated serving cellused as a path loss reference, and a prohibitPHR-Timer expires; or theprohibitPHR-Timer expires, and path loss (dB) increases much more in atleast one activated serving cell used as a path loss reference after aterminal secures uplink resources for new transmission and performs thelast transmission of PHR, PHR is triggered. A terminal can measure thepath loss on the basis of RSRP.

: prohibitPHR-Timer expires or has expired and the path loss has changedmore than dl-PathlossChange dB for at least one activated Serving Cellwhich is used as a pathloss reference since the last transmission of aPHR when the UE has UL resources for new transmission;

2. In case a periodicPHR-Timer expires, PHR is triggered. Since PHchanges in a random fashion, according to a periodic PHR scheme, aterminal triggers PHR when the periodicPHR-Timer expires, and if PR isreported, the terminal activates the periodicPHR-Timer again.

: periodicPHR-Timer expires;

3. In case configuration or reconfiguration related to the PHR operationexcept for prohibition of the PHR is performed by the higher layer suchas RRC or MAC, PHR is triggered.

: upon configuration or reconfiguration of the power headroom reportingfunctionality by upper layers, which is not used to disable thefunction;

4. In case a secondary serving cell configured for uplink is activated,PHR is triggered.

: activation of an SCell with configured uplink;

5. In case a terminal secures uplink resources for new transmission, andresources are allocated for uplink transmission at the time of uplinkdata transmission or PUCCH transmission through uplink resources duringthe corresponding TTI in any of activated serving cells configured foruplink since the last transmission of a PHR, PUCCH transmission isperformed in the corresponding cell, or the required power backoff(P-MPRc) due to power management since the last transmission of a PHRchanges more than “dl-PathlossChange” [dB], PHR is triggered.

: prohibitPHR-Timer expires or has expired, when the UE has UL resourcesfor new transmission, and the following is true in this TTI for any ofthe actived Serving Cells with configured uplink:

-   -   there are UL resources allocated for transmission or there is a        PUCCH transmission on this cell, and the required power backoff        due to power management (as allowed by P-MPRc) for this cell has        changed more than dl-PathlossChange dB since the last        transmission of a PHR when the UE had UL resources allocated for        transmission or PUCCH transmission on this cell;

As one example of triggering, in case a terminal receives resources fornew transmission during the corresponding TTI, the following three stepsare performed.

(1) In the case of the first uplink resource allocation for newtransmission since the last MAC reset, a periodicPHR-Timer is started.

(2) In case at least one PHR has been triggered since the lasttransmission of a PHR, or a transmitted PHR is the first triggered PHR,and allocated uplink resources provide space enough for transmitting PHRMAC control elements (including an extended PHR), the following schemeis performed.

1) If an extended PHR has been configured, it indicates that each uplinkis configured. If a type 1 PH value is obtained with respect to anactivated serving cell, and a terminal has received uplink resources foruplink transmission through the corresponding serving cell during thecorresponding TTI, the terminal obtains a value corresponding toP_(CMAX,c) field from the physical layer, generates an extended PHR MACCEs (Extended Power Headroom Report MAC Control Elements), and transmitsthe generates extended PHR MAC CEs.

2) If an extended PHR has been configured, and simultaneousPUCCH-PUSCHis configured, a terminal obtains a type 2 PH value with respect to aprimary serving cell. If the terminal performs PUCCH transmission duringthe corresponding TTI, the terminal obtains a value corresponding to theP_(CMAX,c) field from the physical layer. And the terminal generates anextended PHR MAC CE and transmits the generated extended PHR MAC CE.

3) if an extended PHR has not been configured, a terminal obtains a type1 PH value from the physical layer, generates a PHR MAC control element,and transmits the generated PHR MAC control element.

(3) A terminal starts or restarts a periodicPHR-Timer, starts orrestarts a prohibitPHR-Timer, and cancels all of the triggered PHRs.

Meanwhile, an extended PHR MAC CE is checked by the LCID within asub-header. The extended PHR MAC CE can have various sizes.

FIG. 15 illustrates one example of an extended PHR MAC CE.

With reference to FIG. 15, Ci field indicates the secondary serving cellindex (SCellIndex) i; in the case of “1”, it indicates that a PH valueis reported on the corresponding SCell while, in the case of “0”, a PHvalue is not reported on the corresponding SCell. R field is a reservedbit and set to 0.

Also, V field is an indicator indicating whether a PH value is based onactual transmission, or a PH value is related to a reference format. Inthe case of type 1 PHR, if V=0, it indicates that there is actual PUSCHtransmission while, if V=1, it indicates that a PUSCH reference formatis used. In the case of type 2 PHR, if V=0, it indicates actual PUCCHtransmission while, if V=1, it indicates that a PUCCH reference formatis used. If V=0 for both of the type 1 and the type 2 PHR, it indicatesthat P_(CMAX,c) field is defined while, if V=1, it indicates thatP_(CMAX,c) field is not used.

PH (Power Headroom) field is related to a PH value and can comprise 6bits.

P field indicates whether a terminal has applied power backoff due topower management (P-MRP), and P is set to 1 (P=1) in case the P_(CMAX,c)field has a different value by the power backoff.

P_(CMAX,c) field indicates P_(CMAX,c) or {tilde over (P)}_(CMAX,c) usedfor calculation of the PH field above, and this field may or may not bedefined.

Table 8 below shows a nominal terminal transmission power level withrespect to an extended PHR.

TABLE 8 P_(CMAX,c) Nominal UE transmit power level 0 P_(CMAX,c)_00 1P_(CMAX,c)_01 2 P_(CMAX,c)_02 . . . . . . 61 P_(CMAX,c)_61 62P_(CMAX,c)_62 63 P_(CMAX,c)_63

<Disclosure of the Present Specification>

The present specification discloses a method for configuring ortransmitting PHR for each cell or cell group when a User Equipment (UE)or a terminal exchanges information or channels related to controland/or data through two or more cell groups (eNodeB groups) atgeographically different locations.

More specifically, a situation in which cells or cell groups atdifferent geographic locations exchange signals or channels related tocontrol and/or data can be taken into account in the next version of thesystem.

At this time, scheduling information among cells or cell groups atdifferent geographic locations may not be shared dynamically but can beperformed independently; in this case, transmission of each UplinkControl Information (UCI) to the corresponding dedicated cell can betaken into account.

In other words, transmitting UCI about a first base station (eNodeB1) tothe first base station and transmitting UCI about a second base station(eNodeB2) to the second base station can be taken into account.

In this case, it can be described that dual connectivity has beenestablished for a terminal connected to both of the first and the secondbase station.

In the case of dual connectivity, a terminal can be additionallyconnected to a small cell or a small cell base station (SeNB)simultaneously to perform data boosting with a macro base station (MeNB)responsible for RRC configuration and voice communication.

The disclosure of the present specification assumes that a macro basestation (eNodeB) is set to a master cell group (MCG), and a small cellbase station (eNodeB) is set to a secondary cell group (SCG).

Also, an MCG includes a PCell (Primary Cell), and an SCG includes apSCell (Primary Small Cell) for transmitting PUCCH and the correspondingUCI to an SeNB. However, the technical principles of the presentinvention are not limited to an embodiment but can be extended to asituation in which information or channels related to control and/ordata are exchanged with two or more cells connected through a non-idealbackhaul.

In the next version of the system, it can be taken into account that aUCI corresponding to an MCG is transmitted by a UE to an MeNB of theMCG, and a UCI corresponding to an SCG is transmitted by a UE to anSeNB.

Also, it can be configured that RRM (Radio Resource Management) such asRSRP/RSRQ is performed for all of the serving cells, and correspondingreport about the result is transmitted only to the MeNB responsible forRRC configuration.

Also, in the next version of the system, it can be taken into accountthat a UE performs PHR (Power Headroom Reporting) for all of the servingcells and transmits measurement or calculation values with respect toall of the serving cells to both of the MeNB and SeNB.

Taking into account the fact that RRM measurement is reported only tothe MeNB and the functions performed by the MeNB (RRC configuration,mobility handling, and so on), the PHR transmitted to the MeNB and SeNBby the UE can be configured differently.

More specifically, the corresponding PHR configuration information canselect virtual PH irrespective of scheduling and actual PH for which PHis calculated (or calculated by taking into account actual transmission)according to the scheduling.

The present specification discloses a method for configuring atransmission target of a UE differently as an MeNB or an SeNB forconfiguring the PHR.

In what follows, the present specification will be described in moredetail. In the first disclosure of the present specification, a methodfor transmitting a PHR to an MeNB is described, in the second disclosureof the present specification, a method for transmitting a PHR to an SeNBis described, in the third disclosure of the present specification, amethod for configuring a virtual PH is described, in the fourthdisclosure of the present specification, a method for configuringP_(CMAX,c) corresponding to PHR calculation is described, in the fifthdisclosure of the present specification, a method for configuring PHR inthe asynchronous case is described, and in the sixth disclosure of thepresent specification, a method for transmitting a PHR in the case ofPHR triggering is described.

<First Disclosure of the Present Specification—PHR to MeNB>

As described above, in the first disclosure of the presentspecification, methods for transmitting a PHR to an MeNB will beexplained.

By default, a PH value is determined by the information configured by ahigher layer, TPC (Transmit Power Control) informed to a user equipmentthrough a DCI, an amount of path loss estimated by the UE, andscheduling information of the UE.

In the description above, it can be assumed that accurate informationabout TPC, path loss, and scheduling is not shared in a dualconnectivity mode.

However, if it is taken into account that RRM measurements of all of theserving cells including an SCG are transmitted to the MeNB, the MeNB canestimate the path loss with respect to the SeNB on the basis of the RSRPcorresponding to the SeNB.

In other words, in case a PH with respect to the SeNB is calculatedaccording to actual scheduling at the time of configuring a PHR to betransmitted to the MeNB, the MeNB can estimate information aboutscheduling of the SeNB on the basis of a received PH and P_(CMAX,c) orcan perform scheduling of the MeNB or power allocation efficiently bytaking into account actual PH.

A method for configuring a PHR to be transmitted to the MeNB is asfollows.

—1-1 Configuration Method

The 1-1 configuration method refers to the method for a UE to calculatePH according actual scheduling at the time of calculating PH withrespect to an SeNB to be transmitted to an MeNB.

In the absence of scheduling, a virtual PH can be calculated by using areference format or under the assumption that MPR=0 (refer to the Rel-11specification, 3GPP TS 36.213, 3GPP TS 36.321)

Also, path loss related to the SeNB incurred at the time of calculatingthe PH can be calculated by using a recent RSRP reported to the MeNB.

—1-2 Configuration Method

The 1-2 configuration method refers to the method for a UE to calculatevirtual PH by using a reference format or assuming that MPR=0irrespective of actual scheduling at the time of calculating PH withrespect to an SeNB to be transmitted to an MeNB (refer to the Rel-11specification, 3GPP TS 36.213, 3GPP TS 36.321).

Also, PH about an MCG in a PHR transmitted to the MeNB can be obtainedby calculating actual PH according to actual scheduling.

<Second Disclosure of the Present Specification—PHR to SeNB>

As described above, methods for transmitting a PHR to an SeNB accordingto the second disclosure of the present invention will be explained.

In case an RRM measurement result of all of the serving cells includingan SCG is transmitted to an MeNB, the SeNB is still unable to accuratelyestimate the PH value by using TPC informing the UE through a DCI withrespect to the MeNB, an amount of path loss estimated by the UE, andscheduling information of the UE.

In other words, when PH is calculated by using the correspondinginformation, it is not possible to know whether path loss or schedulinggives the corresponding information; therefore, it may be inefficient touse actual PH with respect to the MeNB for subsequent scheduling withrespect to the SeNB or power allocation with respect to a UL channel.

Therefore, in contrast to the MeNB, for the case of a PHR transmitted tothe SeNB, virtual PH may be taken into account irrespective ofscheduling when PH corresponding to an MCG is calculated.

The following describes a method for configuring a PHR to be transmittedto the SeNB.

—2-1 Configuration Method

The 2-1 configuration method calculates virtual PH by using a referenceformat irrespective of actual scheduling or by assuming that MPR=0 whenthe UE calculates PH with respect to the MeNB to be transmitted to theSeNB (refer to the Rel-11 specification).

—2-2 Configuration Method

The 2-2 configuration method calculates PH according to actualscheduling when the UE calculates PH with respect to the MeNB to betransmitted to the SeNB.

More specifically, according to the 2-2 configuration method, in theabsence of scheduling, virtual PH can be calculated by using a referenceformat or by assuming that MPR=0 (refer to the Rel-11 specification).

Also, calculating actual PH according to actual scheduling can be takeninto account for the PH with respect to an MCG in the PHR transmitted tothe SeNB.

As described in the first and the second disclosure above, calculationof virtual PH can be taken into account irrespective of scheduling forthe PH with respect to an SCG in the PHR transmitted to an MeNB, andcalculation of actual PH can be taken into account according toscheduling for the PH with respect to an MCG in the PHR transmitted toan SeNB.

<Third Disclosure of the Present Specification—Method for ConfiguringVirtual PH>

As described above, methods for configuring virtual PH according to thethird disclosure of the present specification will be explained.

A reference format can be configured through higher layer signaling oremploy a default format assumed in the absence of higher layersignaling.

The reference format may include MCS (Modulation Coding Scheme),resource allocation, and so on; or may be determined on the basis ofstatistics received by a terminal through a recent uplink grant.

For example, if 20 RBs have been scheduled (statistically) through 16QAM during a recent interval, a terminal can determine the referenceformat by using the scheduling.

Similarly, the reference format may be specified by using one of aplurality of reference formats according to a PHR reporting triggercondition. In this case, the reference format can be determined by theterminal or through higher layer signaling.

Also, the method for configuring a reference format described above canalso be applied to a combination of an MeNB PCell and SeNB sPCell (PUCCHcell). In this case, it can be assumed that a PHR about other carriersincludes actual PH or virtual PH.

In other words, virtual PH with respect to an MeNB PCell, referenceformat based virtual PH, or actual PH can be applied when a PHR is givento the SeNB with respect to a PCell; and virtual PH with respect to anSeNB sPCell, reference format based virtual PH, or actual PH can beapplied when a PHR is given to the MeNB with respect to the PCell.

In another method, configuring each serving cell to enable configuringvirtual PH, reference format based virtual PH, or actual PH may also betaken into account. The corresponding configuration can take intoaccount the case in which an MeNB informs an SeNB through signaling.

In the description above, in case virtual PH is yet calculated in thepresence of actual scheduling, it can be taken into account that the UEtransmits P_(CMAX,c) to the base station together when a PHR istransmitted.

<Fourth Disclosure of the Present Specification—Method for ConfiguringP_(CMAX,c) Corresponding to Calculation of PHR>

As described above, methods for configuring P_(CMAX,c) corresponding tocalculation of a PHR according to a fourth disclosure of the presentspecification will be explained.

More specifically, the fourth disclosure of the present specification isrelated to a method for calculating or configuring a PHR in case both ofP_(Cmax,eNB)(per eNB maximum power) and P_(Cmax,c) (per CC maximumpower) are configured.

A method for configuring a PHR at the time of calculating PHcorresponding to an MCG with respect to a PHR transmitted to an SeNB isdescribed below.

—3-1 Configuration Method

The 3-1 configuration method always uses P_(Cmax,SeNB) (maximumtransmission power to the SeNB) at the time of calculating PHcorresponding to an MCG with respect to a PHR transmitted to the SeNB.

—3-2 Configuration Method

The 3-2 configuration method uses the minimum value between twoparameters by using min(P_(CmaxseNB) and P_(Cmax,c)) at the time ofcalculating PH corresponding to an MCG with respect to a PHR transmittedto the SeNB.

—3-3 Configuration Method

The 3-3 configuration method always uses P_(Cmax,c) at the time ofcalculating PH corresponding to an MCG with respect to a PHR transmittedto the SeNB.

—3-4 Configuration Method

The 3-4 configuration method uses P_(Cmin,MeNB) in case theP_(Cmin,MeNB) is configured (minimum transmission power to theconfigured MeNB) at the time of calculating PH corresponding to an MCGwith respect to a PHR transmitted to the SeNB.

—3-5 Configuration Method

The 3-5 configuration method uses min(P_(Cmin,MeNB), P_(Cmax,c)) at thetime of calculating PH corresponding to an MCG with respect to a PHRtransmitted to the SeNB.

—3-6 Configuration Method

The 3-6 configuration method uses P_(Cmax)-P_(Cmin,SeNB), P_(Cmax,c)) incase P_(Cmin,SeNB) is configured (minimum transmission power to theconfigured MeNB) at the time of calculating PH corresponding to an MCGwith respect to a PHR transmitted to the SeNB.

—3-7 Configuration Method

The 3-7 configuration method uses min(P_(Cmax)-P_(Cmin,SeNB),P_(Cmax,c)) in case P_(Cmin,SeNB) is configured (minimum transmissionpower to the configured MeNB) at the time of calculating PHcorresponding to an MCG with respect to a PHR transmitted to the SeNB.

Also, described below is a method for configuring a PHR at the time ofcalculating PH corresponding to an SCG with respect to a PHR transmittedto an MeNB.

—4-1 Configuration Method

The 4-1 configuration method always use P_(Cmax,MeNB) (maximumtransmission power to the MeNB) at the time of calculating PHcorresponding to an SCG with respect to a PHR transmitted to the MeNB.

—4-2 Configuration Method

The 4-2 configuration method uses the minimum value of obtainedparameters by using min(P_(Cmax,MeNB) and P_(Cmax,c)) at the time ofcalculating PH corresponding to an SCG with respect to a PHR transmittedto the MeNB.

—4-3 Configuration Method

The 4-3 configuration method always uses P_(Cmax,c) at the time ofcalculating PH corresponding to an SCG with respect to a PHR transmittedto the MeNB.

—4-4 Configuration Method

The 4-4 configuration method uses P_(Cmax)-P_(Cmin,MeNB) in caseP_(Cmin,MeNB) is configured (minimum transmission power to theconfigured MeNB) at the time of calculating PH corresponding to an SCGwith respect to a PHR transmitted to the MeNB.

—4-5 Configuration Method

The 4-5 configuration method uses min(P_(Cmax)-P_(Cmin,MeNB),P_(Cmax,c)) at the time of calculating PH corresponding to an SCG withrespect to a PHR transmitted to the MeNB.

—4-6 Configuration Method

The 4-6 configuration method uses P_(Cmin,SeNB) in case P_(Cmin,SeNB) isconfigured at the time of calculating PH corresponding to an SCG withrespect to a PHR transmitted to the MeNB.

—4-7 Configuration Method

The 4-7 configuration method uses min(P_(Cmin,SeNB), P_(Cmax,c)) in case′ . . . . , . . . . is configured at the time of calculating PHcorresponding to an SCG with respect to a PHR transmitted to the MeNB.

In the description above, it can be assumed for virtual PH that MPR=0dB, A-MPR=0 dB, P-MPR=0 dB, and Δ′.=0 dB.

Also, in case a PHR with respect to activated serving cells belonging toa different cell group (CG) not corresponding to a PHT transmissiontarget is configured in terms of dual connectivity, if virtual PH iscalculated with respect to a reference format, it can be taken intoaccount that actual values are used for calculation without assumingthat MPR=0 dB, A-MPR=0 dB, P-MPR=0 dB, and Δ′.=0 dB in the presence ofactual scheduling; and ′ . . . , . (or the value or parameter selectedin the fourth disclosure of the present specification) used for thecalculation is sent at the time of PHR transmission.

In the description above, in case the value referenced for thecalculation of PH does not change from the assumption that MPR=0 dB,A-MPR=0 dB, P-MPR=0 dB, and Δ′.=0 dB (for example, the value can bePCmax, xeNB or PCmin, xeNB) the value referenced at the time ofcalculating PH (which can be PCmax, xeNB or PCmin, xeNB) may not betransmitted when actual PH value is transmitted even if the MPR ischanged according to actual scheduling information. This can be possiblebecause in this case, a base station knows the corresponding value. Themethod described above can be applied only for the case in which a valuereferenced at the time of calculating PH is smaller than PCMAX,c orsmaller than a threshold value (for example, 2 dB) predetermined by thehigher layer.

<Fifth Disclosure of the Present Specification—PHR Configuration withRespect to Asynchronous Case>

As described above, methods for configuring a PHR with respect to anasynchronous case according to the fifth disclosure of the presentspecification will be explained.

An MeNB and an SeNB can be asysnchronous in dual connectivity mode, andin this case scheduling information, PCmax, an PCmax,c values can bevaried for each overlapping part. Therefore, calculation of PHR (inparticular, in the case of actual PH information) can also be varied.

In this case, PH about a different base station can take into accountcalculating a PHR with respect to the overlapping part succeeding intime with respect to the base station which is a transmission target.

As one example, in case subframe i of an MeNB overlaps with subframe kand subframe k+1 of an SeNB, the PHR to be transmitted from the subframei of the MeNB can be calculated with respect to the overlapping partbetween the subframe i of the MeNB and the subframe k+1 of the SeNB.

Similarly, taking into account the processing time, the PHR can becalculated with respect to the overlapping part preceding in time withrespect to the base station which is a transmission target.

The methods proposed above (determination of a reference for calculatingPH, configuration of the maximum transmission power (PCmax) used forcalculation of PHR, and reference timing) can be utilized in acombination thereof.

As one example, when PH of the MeNB transmitted to the SeNB iscalculated, virtual PH can be calculated, PHR can always includePCmax,c, and timing referenced when actual PH is calculated can bedetermined with respect to the portion of the overlapping part thatcomes later.

<Sixth Disclosure of the Present Specification—Method for Transmitting aPHR at the Time of PHR Triggering>

As described above, methods for transmitting a PHR at the time of PHRtriggering according to the sixth disclosure of the presentspecification will be explained.

A method for transmitting a PHR according to the sixth disclosure of thepresent specification is used for a terminal in dual connectivity withan MCG (Master Cell Group) and an SCG (Secondary Cell Group) in awireless communication system to transmit a PHR (Power Headroom Report),the method comprising triggering a PHR with respect to a serving cellbelonging to the MCG on the basis of a PHR triggering condition and incase the PHR is triggered, transmitting the PHR to a serving cellbelonging to the MCG.

At this time, the PHR can include PH (Power Headroom) informationcorresponding to an activated serving cell belonging to the SCG.

Also, PH information corresponding to an activated serving cellbelonging to the SCG can be either virtual PH information or actual PHinformation determined on the basis of scheduling information of theterminal.

Also, the virtual PH information can be calculated on the basis of apredetermined reference format.

Also, the PHR triggering condition can include a first PHR triggeringcondition and a second PHR triggering condition, wherein the first PHRtriggering condition specifies the case in which the “prohibitPHR-Timer”is expired or has expired; the case in which a terminal secures uplinkresources for new transmission; the case in which any one of activatedserving cells configured for uplink has resources for uplinktransmission, or PUCCH transmission exists in the corresponding cellafter uplink data transmission through the uplink resources in thecorresponding TTI or after the last PHT transmission is performed at thetime of PUCCH transmission; and the case in which the change of powerbackoff request value (P-MPRc: Power Management Maximum Power Reduction)is larger than the “dl-PathlossChange” [dB] value after the last PHRtransmission.

Also, the second PHR triggering condition can include the case in whichthe “prohibitPHT-Timer” is expired or has expired; the case in which aterminal has secures uplink resources for new transmission; and the casein which the path loss after the last PHR transmission has beenperformed is larger than the “dl-PathlossChange” [dB] value about atleast one activated serving cell used as the path loss reference.

Also, the PHT information corresponding to an activated serving cellbelonging to the SCG can be the virtual PH information in case the PHRis triggered according to the first PHR triggering condition.

Also, the virtual PH information can be transmitted together withPCMAX,c which is the maximum transmission power for a terminal withrespect to a serving cell c for which P-MPRc has been applied. In thiscase, the V field value of the PHR MAC can be set to 0.

Also, in case the PH information corresponding to an activated servingcell belonging to the SCG is set to the virtual PH information, thefirst PHR triggering condition can be ignored.

Also, in case the PH information corresponding to an activated servingcell belonging to the SCG is set to the virtual PH information, thesecond PHR triggering condition can be satisfied even if the terminalhas not secured uplink resources for new transmission.

Also, whether the PHR is triggered according to the first PHR conditioncan be determined through higher layer signaling.

Also, a method according to the sixth disclosure of the presentspecification is used for a terminal in dual connectivity with a firstand a second cell group in a wireless communication system to transmit aPHR (Power Headroom Report) through the first cell group, the methodcomprising receiving configuration information of PH (Power Headroom)corresponding to an activated serving cell belonging to the second cellgroup; in case a PHR triggering condition is satisfied, generating thePHR and transmitting the generated PHR to a serving cell belonging tothe first cell group, wherein the PHR is configured to include one ofvirtual PH information about an activated serving cell belonging to thesecond cell group determined on the basis of configuration informationof the received PH and actual PH information determined on the basis ofscheduling information of the terminal.

At this time, the first cell group is an MCG (Master Cell Group), andthe second cell group is an SCG (Secondary Cell Group).

Also, the PHR triggering condition can include the first and the secondPHR triggering condition described above.

Also, the PHR can include the virtual PH information in case the PHR istriggered according to the first PHR triggering condition.

Also, in case the PHR is configured to include the virtual PHinformation, the first PHR triggering condition can be ignored.

Also, in case the PHR is configured to include the virtual PHinformation, the second PHR triggering condition can be satisfied evenwhen the terminal has not secured uplink resources for new transmission.

FIG. 16 is a flow diagram illustrating a PHR transmission methodaccording to one disclosure of the present specification.

According to FIG. 16, a PHR transmission method according to onedisclosure of the present specification comprises the following steps.

First, a terminal according to one disclosure of the presentspecification can transmit a PHR (Power Headroom Report) in a state ofdual connectivity with an MCG (Master Cell Group) and an SCG (SecondaryCell Group) in a wireless communication system and trigger the PHR abouta serving cell belonging to the MCG on the basis of a PHR triggeringcondition S110.

Also, the terminal can transmit a PHR including PH informationcorresponding to an activated serving cell belonging to an SCG to aserving cell belonging to an MCG.

At this time, the PH information corresponding to an activated servingcell belonging to the SCG can be virtual PH information or actual PHinformation determined on the basis of scheduling information of theterminal.

In what follows, a PHR transmission method according to the sixthdisclosure of the present specification will be described in detail.

In the next version of the system, when a PHR is transmitted in the dualconnectivity state, actual PH can be transmitted to an activated servingcell corresponding to another cell group rather than the cell group (CG)corresponding to a target cell for transmission, virtual PH can betransmitted, or either of the actual and virtual PH can be transmittedafter being selected through higher layer signaling. The existing 3GPPRel-11 specification gives the conditions for triggering a PHR asdescribed below.

(1) The case in which “prohibitPHR-Timer” expires or has expired; andthe path loss has changed more than dl-PathlossChange dB for at leastone activated Serving Cell which is used as a pathloss reference sincethe last transmission of a PHR when the UE has UL resources for newtransmission.

: prohibitPHR-Timer expires or has expired and the path loss has changedmore than dl-PathlossChange dB for at least one activated Serving Cellwhich is used as a pathloss reference since the last transmission of aPHR when the UE has UL resources for new transmission;

(2) The case in which a periodic timer expires

: periodicPHR-Timer expires.

(3) The case in which configuration or reconfiguration related to thePHR operation except for prohibition of the PHR is performed by thehigher layer such as RRC or MAC.

: upon configuration or reconfiguration of the power headroom reportingfunctionality by upper layers, which is not used to disable thefunction;

(4) The case in which a secondary serving cell configured for uplink isactivated.

: activation of an SCell with configured uplink;

(5) The case in which “prohibitPHR-Timer” expires or has expired; aterminal secures uplink resources for new transmission; and resourcesare allocated for uplink transmission at the time of uplink datatransmission or PUCCH transmission through uplink resources during thecorresponding TTI in any of activated serving cells configured foruplink since the last transmission of a PHR, PUCCH transmission isperformed in the corresponding cell, or the required power backoff(P-MPRc) due to power management since the last transmission of a PHRchanges more than “dl-PathlossChange” [dB].

: prohibitPHR-Timer expires or has expired, when the UE has UL resourcesfor new transmission, and the following is true in this TTI for any ofthe actived Serving Cells with configured uplink:

-   -   there are UL resources allocated for transmission or there is a        PUCCH transmission on this cell, and the required power backoff        due to power management (as allowed by P-MPRc) for this cell has        changed more than dl-PathlossChange dB since the last        transmission of a PHR when the UE had UL resources allocated for        transmission or PUCCH transmission on this cell;

Under the conditions above, in case P-MPRc changes more than apredetermined value, and PUSCH is used for new transmission, a PHR couldbe transmitted to a base station by reflecting PCMAC,c changed accordingto the P-MPRc through type 1 PH while in the presence of PUCCHtransmission, a PHR could be transmitted to a base station by reflectingPCMAC,c changed according to the P-MPRc through type 2 PH. Also, in theaforementioned case, the PCMAC,c calculated by using the P-MPRc has alsobeen transmitted by being included in the PHR.

However, in the case of dual connectivity, virtual PH can be configuredfor activated serving cells corresponding to another cell group ratherthan a target cell group for PHR transmission, and in this case, PCMAC,c(or a value or a parameter configured in the fourth disclosure of thepresent specification) is calculated by assuming that P-MPRc is 0 dB,and the corresponding PCMAC,c may not be transmitted.

In this case, PHR triggering according to the change of P-MPRc isinefficient, and it is needed that PHR triggering is changedaccordingly.

As one example, suppose a PHR is transmitted to an MCG serving cell. Incase virtual PH is configured for an SCG when an SCG serving cellsatisfies the condition (5), the information about the change of theP-MPRc may not be transmitted to a base station.

In case the condition (1) is applied to serving cells of a differentcell group, and virtual PH is configured for the different cell group,the phrase “when the UE has UL resources for new transmission” can beignored.

Next, in case virtual PH is configured for activated serving cellsbelonging to a different cell group rather than a cell groupcorresponding to the cell to which a PHR is transmitted, a method forconfiguring PHR triggering according to the condition (5) can beimplemented as follows.

—5-1 Configuration Method.

The 5-1 configuration method configures virtual PH when thecorresponding UE prepares a PHR about activated serving cells belongingto a different cell group with respect to the condition (5).

—5-2 Configuration Method

The 5-2 configuration method ignores the condition (5) in case a PHR isconfigured by virtual PH with respect to activated serving cellsbelonging to a different cell group.

In addition, the condition (1) may be ignored. Or in the case of thecondition (1), a PHR can be transmitted even when the phrase “UE has ULresources for new transmission” is not true.

—5-3 Configuration Method

The 5-3 configuration method calculates actual PH even when thecorresponding UE prepares a PHR about activated serving cells belongingto a different cell group with respect to the condition (5) by usingvirtual PH.

—5-4 Configuration Method

The 5-4 configuration method is used for the corresponding UE to composeor configure a PHR by using virtual PH about activated serving cellsbelonging to a different cell group with respect to the condition (5).

In addition, the PCMAC,c value reflecting the P-MPRc can be transmittedtogether with virtual PH. At this time, the field V comprising the PHRcan be set to 0.

More specifically, in this case, a reference format is assumed forcalculating virtual PH, but an actual MPR value can be used forcalculating the PCMAC,c value (or parameter values according to thefourth disclosure of the present specification).

—5-5 Configuration Method

The 5-5 configuration method configures or determines whether to applythe condition (5) through the higher layer.

—5-6 Configuration Method

The 5-6 configuration method configures the operation of the UEaccording to the condition (5) through the higher layer.

More specifically, in case the virtual PH is calculated, and a differentparameter (for example, parameters according to the fourth disclosure ofthe present specification) rather than the PCMAC,c is used, if thecorresponding parameter does not take into account P-MPRc, the condition(5) can be ignored. As one example, in case min(PCmin,SeNB, PCmax,c) isutilized for calculating virtual PH, and PCmin,SeNB is smaller thanPCmax,c, then the UE can ignore the condition (5).

<Additional Disclosure of the Present Specification—Network Operationwith PHR in Dual Connectivity>

In what follows, a network operation about a PHR in dual connectivityaccording to additional disclosure of the present specification will bedescribed.

As described above, a UE can be configured so that a network can alwaysload virtual PH or actual PH on a carrier belonging to a different cellgroup.

In this situation, one base station can adjust its scheduling by usingPH about the carrier corresponding to a different cell group and alsouse the PH for power control coordination between an MeNB and an SeNB.More specifically, the following cases can be taken into account.

-   -   The case in which virtual PH is always configured for a carrier        of a different cell group

In case positive PH is loaded on carrier 1, the corresponding basestation does not know how a different base station is scheduled, andtherefore it is difficult to figure out utilization of power.

According to additional disclosure of the present specification, in casethe MeNB configures the maximum power of the SeNB, or the maximum powerabout the carrier possessed by the SeNB is adjusted through PE_(MAX), ifPH is smaller than a predetermined threshold by taking into account thescheduling of the SeNB with respect to the positive PH, PE_(MAX) isenlarged.

In this case, determining that path loss with respect to the SeNB hasincreased or the situation requires more allocation of power, PCmax,cwith respect to the SeNB carrier can be adjusted through PE_(MAX) orthrough new inter-node RRC signaling.

This indicates that the PE_(MAX) about the corresponding carrier isreconfigured for the terminal, and MeNB can transmit new PE_(MAX) to theSeNB. Also, the SeNB may check its PH and request new PE_(MAX) from theMeNB.

In case negative PH is loaded on the first carrier, and no particularoperation is performed, negative PH without PUSCH scheduling informationindicates that accumulated power has approached or exceeded PCmax,c;thus it can be taken into account that there is no scheduling about thefirst carrier for a while. Therefore, it can be assumed that the powerused for the first carrier can be directed to a different carrier. Forexample, in case the terminal is capable of performing look-ahead basedoperation, 20% of the maximum power of the terminal is reserved for eachcell group such that P_MeNB=20%, P_SeNB=20%, and negative PH is loadedon a carrier with respect to the SeNB, the MeNB can assume that the SeNBis not going to perform scheduling for a while because of powershortage.

In this case, assuming that P_SeNB of 20% can be used from the MCG, theMeNB can perform aggressive scheduling. Also, in case negative PH isloaded with respect to a terminal, it can be assumed that reliabletransmission is not possible due to power shortage; therefore, in theevent of power limited case, a carrier loaded with negative PH can bedropped first.

If negative PH is loaded on its carrier, the SeNB can request the MeNBto increase PCmax,c.

If PE_(MAX) is configured as cell-common according to the maximumcoverage that can be supported by one cell, and negative PH is loadedcontinuously, the MeNB can interpret that the corresponding carrierlacks uplink coverage.

Therefore, if negative PH (virtual PH) is loaded continuously on acarrier of an SCG, the corresponding carrier can be released. Also, ifvirtual PH is negative for this situation, the terminal can trigger aPHR.

-   -   The case in which actual PH is configured for a carrier        belonging to a different cell group

If positive PH is loaded on a first carrier, power utilization may notbe easily figure out since the corresponding base station does not knowscheduling of other base stations.

However, if statistical scheduling information can be exchanged throughbackhaul signaling, it can be helpful. Moreover, if a different basestation is currently increasing power, or increasing accuracy ofscheduling (therefore, information that PH value is going to bedecreased gradually), the corresponding fact can be informed throughbackhaul signaling.

If a different base station is increasing power, the corresponding basestation can adjust aggressiveness of scheduling so that the terminal canavoid a power restriction case.

If it is anticipated that PH is going to be increased gradually, moreaggressive scheduling can be performed in the opposite situation. Tothis purpose, the additional disclosure of the present specificationproposes substituting aggressiveness with backhaul. Or BSR (BufferStatus Report) information can be exchanged periodically. Since a BSRcan inform of the degree of scheduling to be applied afterwards, howmuch power is available can be determined according to the BSR.

Also, in case negative PH is loaded on the first carrier, scheduling ofthe corresponding base station is expected to reduce the amount ofscheduling to lower requested power.

However, since transmission power does not deviate largely from ′ . . .. , . , in this case a base station can configure its power by assumingthat a different base station is using the maximum power.

In the case of an MeNB, if it is required to allocate little power tothe SeNB, MeNB can reconfigure power by lowering the PCmax,c (PEMAXreconfiguration).

To achieve effective operation as described above, an additionaldisclosure of the present specification proposes that each base stationis enabled to configure PH reporting type (always virtual PH or actualPH) of a different base station group. In other words, the MeNB canconfigure an SeNB carrier to have actual PH, and the SeNB can configurean MeNB carrier to always have virtual PH. Also, each carrier can befurther configured to have actual PH or virtual PH.

The additional disclosure of the present specification proposesexchanging the following information between base stations to achieveeffective operation.

(1) Traffic condition statistics, for example, coherent time: indicateshow long a traffic condition is maintained.

-   -   Configuration of virtual PH may always be disabled.

(2) Aggressive scheduling indicator: it indicates whether to changescheduling information (whether to increase the amount of data) to useall of the corresponding power in case actual PH is positive.

(3) Power statistics per each base station or activated serving cell(actual power or requested power)

(4) Packet information of the corresponding transmission (the wholesize, the amount of transmitted data, the amount of remaining data, droprate, BER (Bit Error Rate), FER (Frame Error Rate), and so on)

(5) Statistics about scheduling information: RB allocation (the numberof RBs, RB form, and so on), modulation, and transmission (Tx) scheme.

(6) Path loss statistics can include path loss coherent time.

FIG. 17 is a block diagram illustrating a wireless communication systemin which the disclosure of the present specification is implemented.

A base station 200 includes a processor 201, memory 202, and RF (RadioFrequency) unit 203. The memory 202, being connected to the processor201, stores varies types of information required for driving theprocessor 201. The RF unit 203, being connected to the processor 201,transmits and/or receives a radio signal. The processor 201 implements aproposed function, process, and/or method. In the embodiment describedabove, the operation of a base station can be realized by the processor201.

A terminal includes a processor 101, memory 102, and RF unit 103. Thememory 102, being connected to the processor 101, stores varies types ofinformation required for driving the processor 101. The RF unit 103,being connected to the processor 101, transmits and/or receives a radiosignal. The processor 101 implements a proposed function, process,and/or method.

The processor can include ASIC (Application-Specific IntegratedCircuit), other chipsets, logical circuit and/or data processingapparatus. The memory can include ROM (Read-Only Memory), RAM (RandomAccess Memory), flash memory, memory card, storage medium and/or otherstorage apparatus. The RF unit can include a baseband circuit forprocessing a radio signal. In case embodiments are implemented bysoftware, the methods described above can be implemented in the form ofmodules (processes or functions) performing the functions describedabove. A module is stored in the memory and can be executed by theprocessor. The memory can be installed inside or outside the processorand can be connected to the processor through various well-known means.

A terminal according to one disclosure of the present specificationtransmits PHR (Power Headroom Report) with dual connectivity to an MCG(Master Cell Group) and SCG (Secondary Cell Group) in a wirelesscommunication system according to the disclosure of the presentspecification comprises an RF unit; and a processor triggering PHR abouta serving cell belonging to the MCG according to PHR triggeringconditions and in case the PHR is triggered, controlling the RF unit totransmit the PHR to the serving cell belonging to the MCG, wherein thePHR includes PH (Power Headroom) information corresponding to anactivated serving cell belonging to the SCG, and PH informationcorresponding to the activated serving cell belonging to the SCG iseither virtual PH information or actual PH information determined on thebasis of scheduling information of the terminal.

Also, the virtual PH information can be calculated on the basis of apredetermined reference format.

Also, the PHR triggering condition can include a first PHR triggeringcondition and a second PHR triggering condition, wherein the first PHRtriggering condition specifies the case in which the “prohibitPHR-Timer”is expired or has expired; the case in which a terminal secures uplinkresources for new transmission; the case in which any one of activatedserving cells configured for uplink has resources for uplinktransmission, or PUCCH transmission exists in the corresponding cellafter uplink data transmission through the uplink resources in thecorresponding TTI or after the last PHT transmission is performed at thetime of PUCCH transmission; and the case in which the change of powerbackoff request value (P-MPRc: Power Management Maximum Power Reduction)is larger than the “dl-PathlossChange” [dB] value after the last PHRtransmission. The second PHR triggering condition can include the casein which the “prohibitPHT-Timer” is expired or has expired; the case inwhich a terminal has secures uplink resources for new transmission; andthe case in which the path loss after the last PHR transmission has beenperformed is larger than the “dl-PathlossChange” [dB] value about atleast one activated serving cell used as the path loss reference.

Also, PH information corresponding to an activated serving cellbelonging to the SCG can be configured to have the virtual PHinformation in case the PHR is triggered according to the first PHRtriggering condition.

Also, in case PH information corresponding to an activated serving cellbelonging to the SCG is configured to include the virtual PHinformation, the first PHR triggering condition can be ignored.

Also, in case PH information corresponding to an activated serving cellbelonging to the SCG is configured to include the virtual PHinformation, the second PHR triggering condition can be satisfied evenwhen a terminal has not secured uplink resources for new transmission.

Also a terminal according to one disclosure of the present specificationhas dual connectivity to a first and a second cell group and transmitsPHR (Power Headroom Report) through the first cell group, the terminalcomprising an RF unit receiving configuration information of PH (PowerHeadroom) corresponding to an activated serving cell belonging to thesecond cell group; and a processor controlling the RF unit to generatethe PHR and transmit the generated PHR to a serving cell belonging tothe first cell group in case conditions for triggering PHR aresatisfied, wherein the PHR can be configured to include any one ofvirtual PH information about an activated serving cell belonging to thesecond cell group based on configuration information of the received PHand actual PH information determined on the basis of schedulinginformation of the terminal.

At this time, the first cell group can be an MCG (Master Cell Group),and the second cell group can be an SCG (Secondary Cell Group).

According to the disclosure of the present specification, a PHR can beconfigured in the dual connectivity state, and transmission can beconfigured efficiently.

More specifically, according to the disclosure of the presentspecification, a terminal in the dual connectivity state can perform PHRtransmission efficiently by applying virtual PH information according toscheduling and a PHR triggering condition.

According to the disclosure of the present specification, theaforementioned problem in the prior art can be solved. Morespecifically, according to the disclosure of the present specification,a terminal with dual connectivity can perform PHR transmissionefficiently by applying virtual PH information according to schedulingand PHR triggering conditions.

In the system described above, methods have been described on the basisof a flow diagram by using a series of steps or blocks; however, thepresent invention is not limited to the specific order of steps, andsome of the steps can be performed in a different order from thedescription or performed simultaneously. Also, it should be clearlyunderstood by those skilled in the art that the steps shown in the flowdiagram are not exclusive to each other, but different steps can beincluded therein, or one or more steps in the flow diagram can beremoved without affecting the technical scope of the present invention.

What is claimed is:
 1. A method for transmitting a power headroom report(PHR), the method performed by a terminal and comprising: receiving, bythe terminal with dual connectivity to two cell groups, a configurationof a PHR mode; generating, by the UE, the PHR based on the receivedconfiguration of the PHR mode; and transmitting the generated PHR to aserving cell belonging to one cell group among the two cell groups,wherein the PHR mode indicates whether a mode for computing a powerheadroom for the other cell group is a real mode or a virtual mode, andwherein if the mode for computing the power headroom is the virtualmode, the PHR is generated by computing the power headroom based on anassumption that at least one of PUSCH and PUCCH is not transmitted onany serving cell of the other cell group.
 2. The method of claim 1,wherein if the mode for computing the power headroom is the virtualmode, the power headroom is computed based on a predetermined referenceformat.
 3. The method of claim 1, wherein if the mode for computing thepower headroom is the real mode, the generating the PHR includescomputing the power headroom based on a real transmission of the atleast one of PUSCH and PUCCH.
 4. The method of claim 1, wherein ifcondition for triggering the PHR is satisfied, the PHR is generated andtransmitted to the serving cell belonging to the one cell group.
 5. Themethod of claim 1, wherein the one cell group is a MCG(Master CellGroup) and the other cell group is a SCG(Secondary Cell Group).
 6. Aterminal for transmitting a power headroom report (PHR), the terminalcomprising: a transceiver configured to establish a dual connectivity totwo cell groups; and a processor configured to control the transceiverand to perform: receiving a configuration of a PHR mode; generating thePHR based on the received configuration of the PHR mode; andtransmitting the generated PHR to a serving cell belonging to one cellgroup among the two cell groups, wherein the PHR mode indicates whethera mode for computing a power headroom for the other cell group is a realmode or a virtual mode, and wherein if the mode for computing the powerheadroom is the virtual mode, the PHR is generated by computing thepower headroom based on an assumption that at least one of PUSCH andPUCCH is not transmitted on any serving cell of the other cell group. 7.The terminal of claim 6, wherein if the mode for computing the powerheadroom is the virtual mode, the power headroom is computed based on apredetermined reference format.
 8. The terminal of claim 6, wherein ifthe mode for computing the power headroom is the real mode, thegenerating the PHR includes computing the power headroom based on a realtransmission of the at least one of PUSCH and PUCCH.
 9. The terminal ofclaim 6, wherein if condition for triggering the PHR is satisfied, thePHR is generated and transmitted to the serving cell belonging to theone cell group.
 10. The terminal of claim 6, wherein the one cell groupis a MCG(Master Cell Group) and the other cell group is a SCG(SecondaryCell Group).